The Yellow Jackets (4-2) have won two of three.
OD Anosike scored 13 points and freshman point guard Evan Hymes added three for Siena (2-2), which has lost two straight.
First-year Georgia Tech coach Brian Gregory suspended Rice for the first three games this season for violating an undisclosed team rule. The junior swingman has responded, however, with a 17.7 scoring average in three games, all as a reserve, since he returned.
Rice, who hit his first seven shots and finished 10 of 12 from the field, stole the ball from Kyle Downey on Siena's perimeter and dunked for a 28-13 lead at the 5:56 mark of the first half.
Rice started 23 of his 31 games as a sophomore last season, but might stay in a reserve role, Gregory said after the game.
Siena was without three key players — point guard Rakeem Brookins, forward Owen Wignot and forward Trenity Burdine — so the Saints had a short bench.
Hymes began the game with a team-best 19.3 scoring average, but struggled to get open looks at the basket against the defense of Mfon Udofia and Pierre Jordan. Hymes was 1 of 9 from the field and missed all three of his shots in the second half, but he finished with a game-high six assists.
Siena, which went 13-18 last season, was coming off a 64-58 home loss Monday to St. Bonaventure.
The Yellow Jackets finished sixth in the Charleston Classic last weekend, losing to St. Joseph's, beating VCU and losing 59-50 on Sunday to LSU.
Daniel Miller and Julian Royal each scored six points for Georgia Tech.