[4] During his high school years, Fabien Roussel engaged in the Mouvement Jeunes Communistes de France (MJCF) to denounce the apartheid in South Africa and demanded the release of Nelson Mandela.

He also participated in major demonstrations against the Monory law and Devaquet bill, related respectively to employee shareholding and university organisation.

From 1997, he was advisor in charge of communication for Communist Michelle Demessine, then Secretary of State for Tourism under Prime Minister Lionel Jospin.

In September 2023, Fabien Roussel had launched a call "to invade gas stations and supermarkets" , considering that it was "self-defense" in the face of rising prices.

"There are concrete measures to implement to lower prices, block them at the bottom (...) We are calling for mobilization, to invade gas stations, supermarkets, prefectures, because the State is responsible ," he justified.

[10] In 2024, Roussel was defeated by the National Rally candidate Guillaume Florquin in the first round of that year’s snap elections, his seat had been held by PCF since 1962.

[11][12] Roussel takes progressive positions on socioeconomic issues and favours raising the minimum wage to €1,500 a month post-tax, as well as reducing the workweek to 32 hours and lowering the retirement age to 60.

Unlike many French leftists, he is strongly supportive of nuclear power and has expressed a positive view of hunting.