Trailing by six at halftime, Colorado State rallied to a 56-54 lead on Tiel Daniels' dunk. But Evans scored eight points amid a 10-2 run and the Aggies were back on top 71-60 with 9:25 to play.
Daniels dunked and the Rams closed to 91-90 with 13 seconds left, but Smith was fouled and made both free throws.
John Gillon made two free throws to pull the Rams within a point, but Rector made three free throws in the final eight seconds to seal it.
Antwan Scott scored a career-high 35 points with eight 3-pointers for the Rams (10-8, 2-3).