Olson had 11 points and 10 rebounds for the Greyhounds (17-8, 9-4 Metro Atlantic Athletic Conference), who held an opponent under 60 points for the 12th time this season.
Both teams got off to slow starts, with the score 8-8 after nearly 6 minutes. Although Loyola built a nine-point lead, the Saints got within one and trailed 30-27 at halftime.
With Siena holding a 37-36 lead with 11:14 left, a jumper by Julius Brooks sparked a 19-5 run putting the Greyhounds comfortably ahead.
Dylon Cormier added 11 points and four steals for Loyola, which made 19 of 30 free throws compared to 10 of 13 for the Saints.
O.D. Anosike led Siena (6-18, 4-9) with 16 points and 16 rebounds.