South Carolina point guard Tre Kelley missed a 3-pointer with about five seconds left as the Gators (18-7, 10-4 in the Southeastern Conference) beat the Gamecocks (14-11, 6-8) for the ninth straight time and 13th time in the last 14 meetings.
The win clinched second place in the SEC Eastern Division for the Gators.
Roberson led Florida with 17 points on 6-of-15 shooting while Powell led all scorers with 18 points and 13 rebounds. Kelley added 17.
Florida scored 10 straight points to go up 15-10 on Matt Walsh's 3-pointer with 11:52 left in the first half, but the Gamecocks used a 21-7 surge in nearly an 8-minute stretch to earn a 37-27 halftime lead.
South Carolina hit five 3-pointers in the run, including back-to-back 3-pointers by Tre Kelley, who had 10 first-half points after hitting just two of nine shots in his last three games. Renaldo Balkman's reverse layup made it 31-22 with 3:30 remaining and capped the surge by the Gamecocks, who held Florida to its fewest points in the first half this season.
The second half was more of the same - at least at the start. The Gamecocks outscored the Gators 9-2 in the first 3:10 behind Powell, who scored on two straight layups after feeding Josh Gonner on the baseline for a layup as South Carolina extended its lead to 46-29.
But the Gators rallied, putting together a 20-4 run that gave them a 62-61 lead on Matt Walsh's 3-pointer with 2:34 left. The Gamecocks went without a field goal for nine minutes, missing all six shots and committing five turnovers.