Rosen was placed on waivers by the Blues on Sunday, PuckPedia reports.
Rosen hasn't appeared in a regular-season NHL game since the 2023-24 campaign, and he appears set to begin the upcoming campaign in the minors as long as he clears waivers. The 32-year-old recorded eight goals, 23 assists and 24 PIM across 61 regular-season appearances with AHL Springfield last year.