From Mike Sando's blog
San Francisco: The 49ers released return specialist Allen Rossum and submitted a waiver claim for Seahawks defensive tackle Michael Bennett. The NFL awarded Bennett to the Bucs, who had waiver priority based on an inferior record. The 49ers activated receiver Michael Crabtree to make sure the team had 53 players on its roster. Failing to keep 53 players on the roster would have forced the team to release Dominique Zeigler from its practice squad.
At first I thought he meant the RB, but I don't know anything about this Bennett.