J.J. Avila finished with 23 points, seven rebounds and four steals for Colorado State (14-2, 1-2), which dropped its second straight after opening the season 14-0.
Wyoming moved out to a 13-point lead in the second half after a pair of 3-pointers from Hankerson. The Rams chipped away to pull within one with 4:01 remaining after a split pair of free throws from Stanton Kidd.
Nance made a layup and followed Avila's lay-in with a dunk to make it 56-52 with 1:38 left. McManamen came up with a late steal before draining his clinching 3-pointer.