In 1925, Roman joined the Ukrainian Military Organization UVO. In 1926, Shukhevych was ordered to assassinate the Lviv school superintendent Stanisław Sobiński accused of polonization of Ukrainian education system. The assassination was carried out by Roman Shukhevych and Bohdan Pidhainy on October 19, 1926.

In February 1929, the Organization of Ukrainian Nationalists was founded in Vienna. Shukhevych under the name "Dzvin" (Bell) became a representative of the Ukrainian Executive.

He was a leader of a wave of attacks against Polish property and homes in Galicia in 1930 intended to provoke Polish authorities into retaliation and radicalise Ukrainian society. Polish administration retaliated with a process of "pacification" which intensified anti Polish sentiment and increased the interest in Ukrainian nationalism.

Shukhevych continued to plan and also participate in terrorist activities and assassinations (sometimes claimed by Ukrainian Nationalists to be acts of protest against anti Ukrainian policies). These included:

• The co-ordination of a series of expropriations from Polish government offices in order to fund continued insurrection in the struggle for Ukrainian national determination, i.e. bank robberies and assaults on postal offices or wagons.
• September 1, 1931 assassination of Tadeusz Hołówko, a moderate Polish politician, who advocated cultural autonomy for Ukrainians. His murder caused a shock and was condemned by both societies.
• The assassination on March 22, 1932 of the Police commissioner Czechowski
• The unsuccessful assassination attempt of the Soviet consul in Lviv as a protest for the Holodomor in Central Ukraine which was done by Mykola Lemyk who mistakenly assassinated the Special emissary of the NKVD Alexiy Mayov.
• The assassination of the minister of internal affairs Bronisław Pieracki, who was declared by the OUN to be the main person responsible for organizing and executing the "pacification" and called the "hangman of the Ukrainian nation". The assassination was carried out July 15, 1934 in Warsaw by Hryts Matseiko.
• On 30 November 1932 Shukhevych participated in an assault on the post office in Gródek Jagielloński, where a number of innocent civilians were killed.

Shukhevych together with Stepan Bandera, Stepan Lenkavsky, Yaroslav Stetsko, Yaroslav Starukh and others developed the concept of "permanent revolution". According to their thesis the Ukrainian people being exploited by an occupier could only obtain freedom through continued pressure on the enemy. As a result the OUN took on the responsibility of preparing for an All-Ukrainian revolt. Shukhevych propagated the ideas that the revolution was an uncompromising conflict. The goal of this action was to educate the people to overcome the foe. Shukhevych took an active part in developing a concept regarding the formation of a Ukrainian army. At that time two diametrically opposed arguments existed. The first was to form a Ukrainian army in the Ukrainian diaspora, the second, a national army to be formed in Western Ukraine organized by Ukrainians.

In July 1934, mass arrests took place regarding the death of Bronisław Pieracki. On July 18 Shukhevych was arrested and July 6–7 he was sent to the Bereza Kartuska Concentration Camp. In the camp he organized a Ukrainian self defense group. In December 1935 he was acquitted and released from the camp for lack of evidence.

During the Warsaw process against the OUN (November 18, 1935 - January 13, 1936) he was called as a witness. Shukhevych stood by his right to speak in Ukrainian for which he was fined 200 zloty. After greeting the court with the call "Glory to Ukraine" he was once again interred.

From January 19, 1935 Shukhevych was confined to the Bryhidka jail in Lviv. He was incriminated for his membership in the Regional executive of the OUN. The lawyer in the process was his uncle: Stepan Shukhevych. Shukhevych was sentenced to 3 years in jail, however, because of the 1935 amnesty he was released from jail after spending half a year in the Bereza Kartuska Concentration Camp and two years in prison.

After being released in 1937, Shukhevych set up an advertising cooperative in March called "Fama" which became a front for the activities of the OUN. Soon outlets were set up throughout Galicia, Volyn and within Poland itself. The workers of the company were members of the OUN, often recently released political prisoners. The company was very successful and had sections working with the press and film, publishing booklets, printing posters, selling mineral water, compiling address listings and also opened its own transportation section.

In November 1938, Carpatho - Ukraine gained autonomy within the Czecho - Slovak state. Shukhevych organized financial aid for the government of the fledgling republic and sent OUN members to set up the Carpathian Sich. In December 1938, he illegally crossed the border from Poland into Czechoslovakia, traveling to the Ukrainian city of Khust. There, with the aid of local OUN members and German intelligence, he set up the General headquarters for the fight against the Czecho - Slovak central government.

Moreover, in January 1939 the OUN decided to throw off the autonomous government, which seemed too much pro - Czechoslovak to them. The coup d'état attempt occurred in the night of March 13 - 14, in the relation to the proclamation of Slovak independence, managed by Germany. With help of sympathizers among the police the insurgents led by Shukhevych captured the weapons of the gendarmerie, but their assaults on garrisons of Czechslovak army failed. Just in the Khust 11 OUN fighters were killed and 51 captured. However, after the Slovak proclamation of independence on March 14 and Nazi's seizure of Czech lands on March 15, Carpatho - Ukraine was immediately invaded and annexed by Hungary. Shukhevych took an active part in the short term armed conflict with Hungarian forces and was almost killed in one of the actions.

After the occupation of Carpathian Ukraine by Hungary was completed, Shukhevych traveled through Romania and Yugoslavia to Austria, where he consulted with OUN commanders and was given new orders and sent to Danzig to carry out subversive activities.

In the Fall of 1939 Shukhevych moved to Kraków with his family where he acted as the contact for the Ukrainian Nationalist Command directed by Andriy Melnyk. He organized the illegal transportation of documents and materials across the Soviet - German border and collected information about OUN activities in Ukraine.

The new political realities required new forms of activity. The Command of the Ukrainian Nationalists could not come to a unified agreement regarding tactics. As a result on February 10, 1940 the organization in Krakow split into two factions - one lead by Stepan Bandera and the other by Andriy Melnyk. Shukhevych became a member of the Revolutionary Command of the OUN headed by Bandera, taking charge of the section dealing with territories claimed by the Ukrainians, which after the Molotov - Ribbentrop pact had been seized by Germany (Pidliashshia, Kholm, Nadsiania and Lemkivshchyna).

A powerful web was formed for the preparation of underground activities in Ukraine. Paramilitary training courses were set up. Military cadres were prepared which were to command a future Ukrainian army. Shukhevych prepared the II Great congress of the OUN which took place in April 1941.

Prior to Operation Barbarossa, the OUN actively cooperated with Nazi Germany. According to the National Academy of Sciences of Ukraine and other sources, OUN-B leader Stepan Bandera held meetings with the heads of Germany's intelligence, regarding the formation of "Nachtigall" and "Roland" Battalions. On February 25, 1941 the head of the Abwehr Wilhelm Franz Canaris sanctioned the creation of the "Ukrainian Legion" under German command. The unit would have had 800 persons. Shukhevych became a commander of the Legion from the OUN-B side. OUN expected that the unit would become the core of the future Ukrainian army. In the spring the OUN received 2.5 million marks for subversive activities against the USSR. In the spring of 1941 the Legion was reorganized into 3 units. One of the units became known as Nachtigall Battalion, a second became the Roland Battalion, a third was inmmidiately dispatched into the Soviet Union for sabotage of the Red Army's rear.

After intensive training the battalion traveled to Riashiv on June 18, and entered Lviv on June 29 where the Act for establishment of the Ukrainian Statehood was proclaimed. The German administration however did not support this act.

At the same time it is estimated that in June – July 1941 over 4,000 Jews were murdered in pogroms in Lviv and other cities in Western Ukraine. There is controversy regarding the participation of the Nachtigall Battalion and Roman Shukhevych in these atrocities, as well as in the Massacre of Lviv professors. The first company of the unit remained in Lviv for only 7 days, while the remainder of the unit joined later during their eastward march towards Zolochiv, Ternopil and Vinnytsia. There are claims that the soldiers of Nachtigall participated in the killing of Jews. During the march at three villages of the Vinnytsia region, Jews were said to have been shot en masse.

The German refusal to accept the OUN-B’s June 30 proclamation of Ukrainian independence in Lviv led to a change of the Nachtigall battalion direction. As the result, Shukhevych together with the battalion was recalled to Germany.

In Germany, in November 1941 the Ukrainian personnel of the Legion was reorganized into the 201 Schutzmannschaft Battalion. It numbered 650 persons who were given individual contracts that required the combatants to serve for one additional year. Roman Shukhevych’s title was that of Hauptmann of the first company and the deputy commander of the Battalion, which was commanded by Yevhen Pobihushchyi.

On March 19, 1942 the Battalion arrived in Belarus where it served in the triangle between Mahiliou - Vitsebsk - Lepel.

With the expiration of the one year contract all the Ukrainian soldiers refused to renew their services. On January 6, 1943 they were sent to Lviv where they arrived on January 8. Roman Shukhevych escaped from arrest by the Gestapo.

Polish - German historian and Holocaust expert Frank Golczewski from the University of Hamburg describes the activities of Schutzmannschaft Battalion 201 at Belarus as “fighting partisans and killing Jews". However, John Paul Himka, a specialist in Ukrainian history during World War II, notes that although units such as the 201 Battalion were routinely used to fight partisans and kill Jews, no one has studied the specific activities of the 201st battalion from this perspective and this ought to be a subject for further study.

More than 2000 partisans were killed by the battalion personnel during it stay in Belarus.

In late 1942, Ukrainian nationalist groups began a campaign of ethnic cleansing of Volhynia, and in early 1944, these campaigns began to include Eastern Galicia. It is alleged that up to 100,000 Polish civilians were murdered, by Ukrainian groups, including the OUN-Bandera, led by Mykola Lebed and then Shukhevych. Shukhevych commanded the UPA during the time when some of those massacres occurred. In August 1943, during III OUN Convention Shukhevych accepted the "Volhynia stategy" (ethnic cleansing) against Poles that was realized by Dmytro Klyachkivsky. As the Supreme Commander of the Ukrainian Insurgent Army he continued anti-Polish action in Eastern Lesser Poland (Eastern Galicia). In April 1944, the main Command of UIA ordered the massive ethnic cleansing of Poles from Galicia.

After escaping from German custody Shukhevych once again headed the Military section of the OUN. In May he became a member of the leadership of the OUN and in time the head. In August 1943 at the III Special Congress of the OUN he was elected head of the Direction of the OUN and Supreme Commander of the Ukrainian Insurgent Army known as UPA.

Under Shukhevych's leadership the evolution of the program for which the OUN fought was further refined. The main principles were

• opposition to all forms of totalitarian systems
• the construction of a democratic state system in Ukraine
• the right for self determination against empire and imperialism.

The Insurgent Army was joined by various people from the Caucasus and Central Asia who had fought in German formations. The rise of non-Ukrainians in the Ukrainian Insurgent Army gave stimulus to the special conference for Captive Nations of Europe and Asia which took place November 21 – 22, 1943 in Buderazh, not far from Rivne. The agenda included the formation of a unified plan for the attack against occupational forces.

During the period of German occupation Shukhevych spent most of his time fighting in the forests, and from August 1944 under Soviet occupation living in various villages in Western Ukraine. In order to unite all Ukrainian national forces to fight for Ukrainian independence Shukhevych organized a meeting between all the Ukrainian political parties. As a result the Ukrainian Supreme Liberation Council (UHVR) was formed.

Shukhеvych died in combat with special units of the MVD near Lviv on March 5, 1950. He was succeeded as leader of UPA by Vasyl Kuk.

Soviet authorities applied the rationale of collective guilt and persecuted all the members of the Shukhevych family. Roman's brother Yuri was murdered at Lviv's Bryhidka Prison just before the German occupation of Lviv. His mother Yevhenia and his wife, Nataliya Berezynska, were exiled to Siberia. His son Yuri Shukhevych and daughter Mariyka were placed in an orphanage. In September 1972, Yuri was sentenced to ten years camp imprisonment and another five years exile after already having spent 20 years in Soviet camps.

According to NKVD officers' memoirs, Roman Shukhevych's body was transported out of Ukraine, burned, and the ashes scattered. This was done on the left bank of the Zbruch River. The unburned remains were thrown into the Zbruch. A commemorative stone cross was erected there in 2003.

According to Vladimir Vyatrovich, a historian specializing in UPA, Natalia Shukhevych, wife of the UPA Head Commander Roman Shukhevych, sheltered in her house a Jewish girl, Irene Reichenberg (other transcription: Reisinberg, Reitenberg) from September 1942 till February 1943. She was a neighbor's daughter and was 7 years old at that time. According to Yuri Shukhevych, at the beginning of the World War II their family lived in Lviv on Queen Yadvyga Street, where their neighbor was a Jewish family of Wolf and Ruzha Reichenberg who owned a textile shop. Nazis shot their older daughter Irma in the street in 1942. Her younger sister Irene lived with the Shukhevych family for a certain period of time while preparing for school. Roman Shukhevych used his connections to provide the girl with new documents in the Ukrainian name of Iryna Vasylivna Ryzhko. The girl's actual birth year was changed from 1936 to 1937. In her new documents Iryna was indicated as a daughter of a Red Army officer killed early in the war. After the arrest of Natalia Shukhevych in 1943 by the Gestapo, Roman Shukhevych took Irene to the orphan shelter at the Ukrainian Greek - Catholic Convent of Vasilianky in the village of Phylypove, near the township of Kulykiv 30 kilometres from Lviv, where Irene remained until the end of World War II surviving German occupation and Holocaust. In 1956 Irene sent a letter with her picture to the prioress of the monastery. After the war Iryna lived in Ukraine and died in 2007 in Kiev at the age of 72. Her son Vladimir still lives in Kiev. Yuri Shukhevych met with him after his mothers death. The Reichenberg family is mentioned in the list of victims of the Nazis at Yad Vashem memorial in Israel.

According to Ukrainian historian and former UPA soldier Lev Shankovsky, immediately upon assuming the position of commander of UPA Shukhevych issued an order banning participation in anti-Jewish activities. No written record of this order, however, has been found.

On Shukhevych's birthdays remembrance mass meetings take place in various Ukrainian cities.

He was portrayed by Ukrainian - Canadian actor Hryhoriy Hladiy in the Ukrainian film Neskorenyi (The Undefeated).

On October 23, 2001 the Lviv Historic Museum converted the house in which Shukhevych was killed into a memorial museum.

Postage stamps and coins have been minted in his honour of the 100th anniversary of his birth. Posthumously, he was awarded the UPA's highest decorations: the Gold Cross of Combat Merit First Class and the Cross of Merit in gold.

Roman Shukhevych was posthumously conferred the title of Hero of Ukraine by President Viktor Yushchenko on October 12, 2007. On February 12, 2009, an administrative Donetsk region court ruled the Presidential decree awarding the title to be legal after a lawyer had claimed that his rights as a citizen were violated because Shukhevych was never a citizen of Ukraine.

President Viktor Yanukovych stated on March 5, 2010 he would make a decision to repeal the decrees to honor the title as Heroes of Ukraine to Shukhevych and fellow nationalist Stepan Bandera before the next Victory Day. Although the Hero of Ukraine decrees do not stipulate the possibility that a decree on awarding this title can be annulled. On April 21, 2010, the Donetsk Administrative Court of Appeals has declared unlawful the former Ukrainian President Viktor Yuschenko's decree of October 12, 2007 to award the Hero of Ukraine title to Roman Shukhevych. The court ruled that the former President had had no right to confer this title to Shukhevych, because Shukhevych had died in 1950 and therefore he had not lived on the territory of independent Ukraine (after 1991). Consequently, Shukhevych was not a Ukrainian citizen, and this title could not be awarded to him. On August 12, 2010 the High Administrative Court of Ukraine dismissed suits to declare four decrees by President Viktor Yanukovych on awarding the Hero of Ukraine title to Soviet soldiers illegal and to cancel them. The filer of this suit stated it was based on the same arguments used by the Donetsk Administrative Court of Appeals on April 21 that deprived Roman Shukhevych the Hero of Ukraine title, as Shukhevych was not a citizen of Ukraine.