In his second full Liiga season in 2018-19, Ruotsalainen (5'8", 179 lbs., 10/29/1997) led Ilves and ranked ninth in the league with 21 goals and added 21 assists to total a team-high 42 points.

He led all Liiga forwards in average ice time (21:05) and faceoffs (1,216) in his 59 regular-season games, posting a faceoff percentage of 54.9%. In seven playoff games in 2019, Ruotsalainen recorded seven points (2+5) and a plus-6 rating. Through parts of four Liiga seasons, he has totaled 73 points (36+37) in 204 regular-season games.

A native of Oulu, Finland, Ruotsalainen won a silver medal with Team Finland at the 2015 IIHF World U18 Championship and represented his country at the 2016 IIHF World Junior Championship. He made his debut with the Finnish national team during the 2018-19 season, joining the team for several games during the Euro Hockey Tour.