Roussel had surgery in March to repair a torn ACL in his right knee, but targeted this game to return because former teammate, friend and mentor Alexandre Burrows was being inducted into the Canucks Ring of Honour in a lengthy pregame ceremony.
Roussel put the Canucks ahead 1-0 at 1:50, taking a 2-on-1 pass from Adam Gaudette and lifting a backhand over a sliding Anders Nilsson, the Senators goalie.
[WATCH: All Senators vs. Canucks highlights]
"I couldn't have written it better," Roussel said. "First shift, first goal, it was awesome. It takes a lot of pressure off my shoulders."
After scoring, Roussel put his hand over his heart and pointed up to the new Burrows tribute.
"I thought if I scored I would give a salute, a little respect to my idol," Roussel said.
Video: OTT@VAN: Roussel puts away great centering feed
Tanner Pearson, Elias Pettersson and Zack MacEwen also scored in the first period, and Thatcher Demko made 40 saves for the Canucks (14-11-4), who are 2-3-0 in the past five games.
"It's just a tremendous person we were able to honor tonight," Demko said of Burrows, who was in the Canucks locker room before the game. "You saw when the ceremony was over, guys were skating hard. We got four quick ones there, obviously he has an effect on our group. He hasn't been around in the room the last couple of years but he's still a heavy name for our group."
Jean-Gabriel Pageau and Tyler Ennis scored for the Senators (11-16-1), who have lost five straight games and been outscored 15-5 in the past three.
"It's on the leaders," Ennis said. "We just weren't ready to go."
Pearson converted a backdoor pass from Christopher Tanev to make it 2-0 at 4:28.
Video: OTT@VAN: Pearson scores tap in from the doorstep
Pettersson, playing his 100th NHL game, tapped in another backdoor pass from Brock Boeser on a power play to make it 3-0 at 13:58. Pettersson has 98 career points (40 goals, 58 assists), but failed to join Pavel Bure (111 points; 64 goals, 47 assists) as the only other player to reach 100 points in their first 100 games with Vancouver.
MacEwen scored his first NHL goal on a deflection in front to increase the lead to 4-0 at 17:23.
"A huge weight off the shoulders," said MacEwen, a 23-year-old forward playing his 11th NHL game. "Being up here the last couple of weeks, getting in a few games and getting some chances, just to get the first one, it feels amazing."
Video: OTT@VAN: MacEwen deflects Benn's shot into the net
Nilsson allowed four goals on 15 shots in the first period and was replaced by Marcus Hogberg, who made 13 saves in relief.
"He's been one of the best goalies in the League and he's been our backbone," Ennis said. "We can't be giving up backdoor tap-ins."
Despite the poor start, the Senators were happy with their effort over the final two periods, outshooting the Canucks 26-14 and forcing Demko to make several hard saves.
"Their goaltender made probably three real five-bell saves in the second there to not let us back in it," Senators defenseman Ron Hainsey said.
Pageau scored on a rebound just above the crease at 11:59 of the second period to cut it to 4-1, and Ennis made it 4-2 with a deflection 40 seconds into the third.
Video: OTT@VAN: Pageau finishes loose puck in front
Oscar Fantenberg scored on point shot to make it 5-2 at 7:34, his first goal with the Canucks.
Fantenberg was beaten to the net by Vladislav Namestnikov for a backdoor tap-in 14 seconds later, but the goal was called back after the Canucks challenged that Namestnikov was offside.
"It took away some momentum, for sure," Ennis said.
They said it
"We probably had more chances offensively than we've had in a month tonight but unfortunately we weren't as good defensively, and that's sometimes what happens. You concentrate on one thing and then another thing goes. We have to play defense in order to have success with this team." -- Senators coach D.J. Smith
"It's a long haul for guys when they come back from an injury like that. Just to see him play, we were happy. To see him score like that, you couldn't script it any better." -- Canucks coach Travis Green on Antoine Roussel scoring in his return from major knee surgery
Need to know
Ottawa goalie Craig Anderson missed his third straight game with an undisclosed injury but practiced Tuesday and could start against the Edmonton Oilers on Wednesday. … Tanev and Gaudette each had two assists. … Vancouver goaltender Jacob Markstrom missed the game to attend his father's funeral in Sweden but is expected back before Saturday's game against the Buffalo Sabres. Michael DiPietro was called up from Utica of the American Hockey League to back up Demko against the Senators. … Canucks defenseman Alexander Edler, who missed his second game with an upper-body injury, was placed on injured reserve Tuesday and will be re-evaluated in two weeks. … Canucks forward J.T. Miller has nine points (four goals, five assists) in a seven-game point streak.
Senators: At the Oilers on Wednesday (9:30 p.m. ET; TVAS, SNW, SNOL, TSN5, NHL.TV)
Canucks: Host the Sabres on Saturday (4 p.m. ET; SN, MSG-B, NHL.TV)
Video: Canucks win 5-2 on night Burrows is honored