Forward Kent Johnson, the No. 5 pick in the 2021 NHL Draft, and undrafted defenseman Nick Blankenburg each made his NHL debut for Columbus after finishing their college careers at the University of Michigan last week.
Blankenburg had an assist on the Blue Jackets' fourth goal by Cole Sillinger in the third period.
"There was a sense of relief when I saw it go in," Blankenburg said. "I'm kind of at a loss of words. It's a childhood dream to play your first game in the NHL, let alone get your first point. As the game went on, I felt like I had a little bit more confidence with the puck."
Roslovic scored at 8:36 of the first period when his shot from the right circle went off Montembeault and over his shoulder.
Columbus outshot Montreal 10-4 in the first.
"We've got to perform. Tonight, we didn't do that," Canadiens defenseman Joel Edmundson said. "Give them credit; they played well, but it should have been a closer game."
Roslovic made it 2-0 at 15:52 of the second period on a redirection from Laine, who gave the Blue Jackets a 3-0 lead 1:30 later on a power play at 17:22, his first goal in 11 games.
"It felt pretty good," Laine said. "We were moving the puck pretty good. Jack tried to go back door to [Gustav Nyquist]. It came off the back wall pretty hot, kind of a tight angle. I'm just happy it went in."