Moulson, a former Islander, tied it for Buffalo 3:07 later when he redirected Jack Eichel's feed from the right circle past Gibson to make it 1-1. It was Moulson's eighth of the season but third in his past six games.
Rodrigues gave the Sabres the lead with his first NHL goal at 17:57 when he made a nifty move against Mayfield and beat Gibson with a wrist shot from the slot. Rodrigues played his second NHL game after making his debut Friday.
"I thought guys came out and played hard, played to win this one and did a real good job right throughout the lineup," Sabres coach Dan Bylsma said. "You don't really think about what [the Islanders are] supposed to do. You're going out there and playing your game and you can't starting thinking, 'OK, they're playing for a playoff spot,' or something like that. We always want to win games, so every game is kind of the same. It's got to be the most important game of the season."