Miles Cartwright added 22 points for the Quakers (14-11, 6-2 Ivy League), who have won three of their last four.
With the Big Red ahead 59-55 with 4:33 left, Rosen made a 3-pointer followed by two free throws to lead 60-59.
Chris Wroblewski’s trey pushed Cornell (10-13, 5-4) back on top, then Rosen knocked down two consecutive 3s for a 66-62 advantage with 1:13 left.
After two free throws by Wroblewski, Cartwright answered with a 3 and Rosen and Cartwright sealed it with two foul shots apiece.
Rosen was 5 of 10 from deep as the Quakers hit 12 of 22 treys. He also had six assists, five rebounds and three steals.
Drew Ferry’s 17 points led Cornell, which lost to Penn 64-52 on Jan. 14.