They were determined not to repeat their poor play in Game 2.
Mats Sundin assisted on both goals for the Maple Leafs, who had 26 shots after managing just 17 Thursday in the 4-2 loss in Game 1.
"I don't think any of us had a very good game the first night out," Belfour said. "We all tried to be better."
Fans chanted "Eddie! Eddie!" throughout as Belfour recorded his 12th career shutout in the playoffs, and his 83rd win, tying him with New Jersey's Martin Brodeur for first place among active goaltenders.
Belfour made his best save during an Ottawa power play in the third period, robbing Daniel Alfredsson of a goal with a glove save.
"Eddie gives us a chance to win every night, and he did it again," Roberts said.
"We tried to be a lot more physical than we were in Game 1. We were a little stiff, a little emotionless," Roberts said. "We were much better in the first. We had some big key hits early in the game."
Ottawa, which went 0-for-6 on the power-play, will host Games 3 and 4 of the best-of-seven Eastern Conference series Monday and Wednesday. The Senators have been eliminated by their provincial rivals in each of their last three playoff meetings.
"They played better, and that's what we expected," Ottawa defenseman Zdeno Chara said. "Eddie was outstanding. We played a good game, but we just didn't score."
Darcy Tucker gave Toronto a spark by returning from a 14-game absence resulting from an abdominal injury. Defenseman Ken Klee also rejoined the lineup, after missing eight games because of a shoulder injury.
"They both gave us a big spark," Toronto defenseman Bryan McCabe said. "Kenny was solid defensively, and Tucker was his usual self, running people over and playing really hard. He's a spark plug, a little pest."
McCabe tied up an Ottawa defenseman before Roberts put a wrist shot between Patrick Lalime's pads at 10:40 of the first.
Roberts made it 2-0 when he scored while Toronto had a two-man advantage.
Just five seconds after Alfredsson received a roughing penalty in the second period, Chara was called for cross-checking. Toronto defenseman Brian Leetch put a slap shot off Lalime before Roberts put the rebound in at 6:02.
Ottawa scored the tying and go-ahead goals on Thursday after Toronto received two consecutive penalties.
Ottawa forward Jason Spezza was a healthy scratch for the second straight game. ... Toronto fans cheered when it was announced that D Aki Berg and LW Mikael Renberg wouldn't play for the Maple Leafs. Berg was a minus-1 in Game 1, and Renberg was even.