The Buckeyes ended a four-game losing streak that came after they had won their first 15 games of the season.
Ohio State fell to Michigan State, Iowa, Minnesota and Nebraska in succession and found itself behind by a point at halftime in this game.
The Fighting Illini were within two points after Tracy Abrams made two free throws with 2:31 to play, but Ross then hit a layup while being fouled and the 3-point play helped the Buckeyes pull away down the stretch.
Lenzelle Smith scored 16 points for the Buckeyes (16-4, 3-4 Big Ten Conference) while Aaron Craft had 11.
Joseph Bertrand delivered 19 points for Illinois (13-7, 2-5 Big Ten).