Joey Dorsey hit all five of his shots, scored 12 points, grabbed 14 rebounds and blocked four shots for Memphis. Robert Dozier had 13 points, 10 rebounds and three blocks as the Tigers (12-0) won their 39th straight home game.
Memphis connected on 11 shots from 3-point range in the first half and built a 25-point lead. The Saints (7-5) could not get any closer than 16 in the second half.
Kenny Hasbrouck led Siena with 18 points, while Edwin Ubiles and Tay Fisher added 14 each.
Siena couldn't muster any offense after an early lead, shooting 32 percent for the game. Even with a short rally to open the second half that cut the deficit to 16, the Saints never threatened, primarily because Memphis answered the rally with a 25-3 run over the next 7 minutes.
The Tigers shot 50 percent outside the arc for the game with Douglas-Roberts missing only one of his six 3-pointers.
Memphis finished with 11 blocks and forced 15 turnovers.
The Tigers used a barrage of 3-point field goals to build a 49-24 halftime lead. They were 11-of-16 from outside the arc, led by Douglas-Roberts, who hit all five of his and had 17 points.
Siena led early as Memphis coach John Calipari was so dissatisfied with the way his starters were playing, he made wholesale substitutions a minute into the game.
The Tigers erased the early deficit with a 10-0 run with Douglas-Roberts recording half of the points. The Tigers added a handful of 3-pointers over the final 3:26 of the half.
Siena was unable to get much offense going outside of Hasbrouck, shooting 31 percent in the first half.
In the second half, Memphis would extend the lead to as many as 46 points with just under 3 minutes left as Calipari emptied his bench.