North Texas (15-13, 6-8 Conference USA) scored 47 points in the second half, overcoming a 32-24 halftime deficit to hand Texas-San Antonio (8-19, 4-10) its third consecutive loss.
North Texas erased the first-half deficit as Williams tied the game at 53 on a 3-pointer with 10:11 left. Walton's basket tied the game again at 55 with 8:36 remaining, sparking an 8-0 run to give the Mean Green a 61-55 lead.
The Roadrunners cut the lead to 66-62 with 1:13 left, but North Texas hit 5 of 6 from the line the rest of the way to secure the win.
T.J. Taylor added 10 points for North Texas.
Edrico McGregor and Keon Lewis each scored 13 to pace the Roadrunners. Devon Agusi added 12.