Ross accounted for 17 points and Smith contributed 16 with five assists as the Buckeyes (19-5, 6-5 Big Ten) corralled a third straight victory.
After falling behind 6-0 to start the game, Ohio State went on a 20-5 run to take the lead for good.
The Boilermakers (14-10, 4-7) lost a fifth in six games.
Kendall Stephens led Purdue with 12 points in a reserve role.
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