"We've all got to chip in and we're going to need that for the remainder of the season to win hockey games," Roberts said.
Roberts and Laraque also had an assist, and Evgeni Malkin scored for Pittsburgh, which scored twice in a 30-second span late in the second period. Erik Christensen finished with two assists.
The Penguins also beat Boston 5-4 in a shootout on Thursday.
P.J. Axelsson and Petteri Nokelainen scored for the Bruins, who have scored more than two goals only once in their last six games. Despite being tied for the third-most points in the Eastern Conference, only three teams in the conference have scored less goals than Boston.
"It's frustrating," Bruins forward Marc Savard said. "You want to score goals. That's the fun of the game: putting the puck in the other team's net. When you're only getting one or two a game, it's frustrating and it weighs on you."
The Bruins scored the first goal for the 22nd time in their 35 games but fell to 15-4-3 in those contests. Zdeno Chara's slap shot from the right point caromed off Pittsburgh goalie Ty Conklin's chest early in the first period, and Axelsson slammed in the rebound.
Roberts tied it 2:16 into the second when he pushed in a feed from Laraque while standing in the slot. It was the 41-year-old's second goal of the season and first since Oct. 17.
"Gary, Christensen and Laraque really set the tone for this game," Pittsburgh coach Michel Therrien said. "They played well."
Malkin's goal was a hard slap shot from above the right face-off circle that went over Bruins goalie Alex Auld's left shoulder and under the crossbar while on the power play 13:04 into the second period. Jordan Staal and Sergei Gonchar assisted on Malkin's 14th goal of the season.
Thirty seconds later, the third line provided some offense again. Laraque scored the 50th goal of his nine-year career -- and second of the season -- when he tapped in Roberts' feed while skating hard to the net on a 2-on-2 to make it 3-1. Christensen had his second assist of the game.
"I like playing with those two guys and hopefully it will keep going," Laraque said.
Nokelainen scored with the goalie pulled for the Bruins with 54 seconds to play, but Roberts had an empty-netter with 10 seconds left.
Conklin, the Penguins' third-string goalie, finished with 28 saves. Both his starts this season are victories over the Bruins.
"It's a game of momentum out there," Axelsson said. "It switches all the time and they took advantage of the momentum they had in the second period. We have got to be better at changing the momentum."
Penguins D Mark Eaton did not play during the third period due to a knee injury. ... The Penguins have had 31 consecutive sellouts at home, a team record. ... Gonchar's assist was the 400th of his career. ... Pittsburgh RW Petr Sykora played in his 800th game.