Rolston, who returned last season for his second stint with the Devils, recorded his 700th NHL point when he scored into an empty net at 19:50. Kovalchuk, acquired from Atlanta on Feb. 4, earned his second assist of the game when he passed up a scoring opportunity to allow Rolston to hit the net.
"We were talking about it before the game and he was right behind me, so why not?" said Kovalchuk, who went straight to the net after Rolston scored to pick up the puck.
"It was a very unselfish play by Kovy to drop that," Rolston said. "He could have obviously shot it in himself, but I'm hoping that I would have gotten to that 700th point."
Martin Brodeur made 25 saves for his 41st victory of the season and New Jersey's 44th.
Jacques Lemaire, who was brought back as Devils coach this season by general manager Lou Lamoriello, extended the team's playoff streak that he began in 1997 before leaving New Jersey after the following season.
"I've been here for all 13 of them and I've seen a lot of guys come and go, but the attitude is the same," Brodeur said. "It starts from our boss upstairs with Lou and it goes and trickles down to the guy that plays the least amount of minutes. We've always had that attitude that the first step is making the playoffs and after that, well, we try to go for bigger things."
The Devils, who have won four straight in Montreal, moved into a tie with Pittsburgh for first place in the Atlantic Division with 93 points.
New Jersey, which snapped a four-game losing streak on the road, holds the edge for second place overall in the Eastern Conference because it has one more win than the Penguins. The Devils have eight games remaining, including Sunday in Philadelphia. Pittsburgh has seven games left.
Andrei Kostitsyn had a goal and an assist, and Tomas Plekanec also scored for the Canadiens, who are sixth in the East with 82 points -- two ahead of Philadelphia and Boston.
Jaroslav Halak stopped 22 shots. Mike Cammalleri had two assists for his first points in three games since returning from a broken leg that sidelined him for 17 games.
Montreal went 0 for 4 with the man advantage.
"The difference in the game was special teams," Canadiens coach Jacques Martin said. "They scored two on the power play and we didn't score any."
Elias scored his 15th goal during New Jersey's 4-on-3 advantage 8:11 in for the only goal of the opening period. Travis Zajac assisted on the goal for his 200th NHL point.
"Right after that first goal deflated us a little bit it got us back in a shell," Montreal forward Brian Gionta said. "For about 10 or 12 minutes, at least, we sat back too much and gave them too much respect."
Langenbrunner gave the Devils a 2-0 lead with another power-play goal 1:59 into the second. The New Jersey captain spun around to get to the puck, after Kovalchuk's point shot failed to get through, and drove a slap shot past Halak from the slot.
Former Devils center Scott Gomez earned his 43rd assist as he helped draw Montreal within 2-1. He fed the puck to Kostitsyn, who snapped a shot past Brodeur for his 15th goal.
Zubrus, who played for Montreal from 1999-2001, restored New Jersey's two-goal advantage at 15:19 when he deflected in Paul Martin's shot for his eighth goal.
Kostitsyn helped get the Canadiens back within one 1:30 later when he banked a centering pass in off Plekanec's right skate.