North Dakota (6-11, 2-4 Big Sky), which snapped a four-game losing streak, trailed 32-25 at halftime, but opened the second half with a 24-5 run and led 49-37 with 10:49 left.
Connor Hill's 3 capped an 8-1 run and cut Idaho's deficit to 62-60 with 2:12 left, but a layup and two free throws by de Rouen pushed North Dakota's lead back to six.
Another 3 by Hill made it 66-63 with 1:31 to play, but Idaho (7-10, 2-4) missed its last five shots.
Hill led Idaho, which has lost four in a row, with 14 points.
North Dakota shot 64 percent in the second half.