The Buccaneers signed Gaines (biceps) on Saturday, Tom Pelissero of NFL Network reports.
Gaines will head to Tampa after recording 36 tackles (16 solo) and four sacks for the Rams last season. The 2019 fourth-round pick underwent a labral and bicep tendon repair back in January, but he is expected to be fully recovered for the offseason and should provide solid depth behind Vita Vea next season.