[4] In June 2017, Roseren endorsed Emmanuel Macron in the 2017 French presidential election, arguing that he would reconnect politics with the lives of citizens.

Roseren was, in return, nominated by Macron's La République En Marche (LREM) in Haute-Savoie's 6th constituency for that year's legislative elections.

He was elected to the National Assembly with 56.5% of the vote in the second round, defeating incumbent deputy Sophie Dion of The Republicans.

[5] In the National Assembly, Roseren focuses on issues surrounding tourism, industry, air quality, urban development and agriculture.

[10] In July 2019, Roseren decided not to align with the majority of his party and became one of 52 LREM deputies who abstained from a vote on the French ratification of the European Union’s Comprehensive Economic and Trade Agreement (CETA) with Canada.