SB Nation's Buccaneers blog, Bucs Nation, examined the reason for the roster move:
Gilberry can play both defensive end and defensive tackle and looked decent during the preseason. Apparently, the Bucs have decided that carrying just four defensive tackles, one of them with injury issues, was a really bad idea.
The 5th-year veteran Gilberry played in 53 games for the Kansas City Chiefs from 2008-2011. In that time he amassed 57 tackles and 14 sacks.
Vandervelde is in his second NFL season out of Iowa. He played in just one game for the Philadelphia Eagles in 2011.