The third-seeded Bobcats (25-7) will play second-seeded Buffalo in Friday's second semifinal. Ohio won both meetings in the regular season.
In the other semifinal, top-seeded Akron will face rival Kent State, the No. 4 seed.
Leading by just two after an awful shooting performance in the first half, Ohio opened the second half with an 11-0 run to take control. The Bobcats, who made just 1 of 14 shots to open the game, pushed their lead to 16 and ended a turnaround season for the seventh-seeded Rockets (18-16).