The Catamounts (12-6, 5-1) have a half-game edge over Albany and the Seawolves (13-5, 4-1), whom they defeated in last season's conference tournament final.
Rusin scored eight points during a 12-0 run early in the second half that gave Vermont a 44-29 advantage.
Stony Brook, after trailing by as many as 18 points, got to within four, 65-61 with 2:48 left, after a dunk by Tommy Brenton. But Sandro Carissimo responded with a layup and two free throws on Vermont's next two possessions for an eight-point lead.
Brian Voelkel had six assists for Vermont, giving him 405 for his career.