Ostler was fortunate to see James Hockley spill a sharp diving chance off Masters, and rubbed salt into Kent wounds with three booming fours off one James Tredwell over.
Sharp, Bennett, James Coppinger and Simon Gillett all had chances for Dean Saunders's side, while the visitors, who slipped down to 16th following the defeat, forced David Button into just one real save.
James held an early shot from Gillett and, after Sharp had fired over the crossbar, was at his acrobatic best to tip George Friend's near-post effort around the post as Rovers created the better first-half chances.