"It's nice to get a win at home, and to do it in overtime is even sweeter," Pominville said.
The Sabres had lost six of their last seven games at home before Friday night's game.
Jason Garrison tallied the lone goal for the Panthers, who failed to secure their first four-game winning streak since 2008.
Florida also attempted to take the points lead in the Eastern Conference with a win. The Panthers haven't held first place in the East after October since Feb. 12, 1997.
Scott Clemmensen stopped 18-of-20 shots in defeat.
In the overtime, Paul Szczechura made a fantastic pass ahead to Pominville, who broke free down the ice. He deked a few times before finishing with a wrister into the lower-right corner.
Roy broke free on a breakaway to put the Sabres on the board first as his wrister from the slot trickled past Clemmensen with 2:10 left in the first period.
Florida took advantage to even the game. Tomas Fleischmann controlled the disc from behind the net before firing a pass to Garrison, who rifled a one-time slap shot from the left circle into the back of the net with 4:12 left in the frame.
This is the second opportunity this season that the Panthers had a chance to win their fourth straight. Florida lost 2-1 in overtime against Tampa Bay on November 25...Buffalo went 0-for-5 on the power play...The Panthers haven't won four in a row since the club recorded a franchise record seven-game winning stretch from March 2-16, 2008.