Ruotsalainen was called into the Finnish national team, added to the roster in the Karjala Tournament on 8 November 2018 at the Hartwall Arena in Helsinki against Russia. While he did not end up with ice time, he made his debut in the next game on 10 November 2018 against the Czech Republic. Ruotsalainen was among the last cuts from the national team for the 2019 World Championships.