Johnsson was drafted by Toronto in the seventh round in 2013. In his second full season with the Marlies, he leads the team with 54 points (26 goals, 28 assists) in 54 games. He will make his NHL debut Wednesday against Dallas.
Rosen, meanwhile, was signed by the Maple Leafs out of Sweden last summer. He appeared in four NHL games earlier in the season, but has since been with the Marlies, recording 17 points in 50 contests.