Roberts arrives from the Florida Panthers, who get defenceman Noah Welch, and Laracque comes over from the Phoenix Coyotes, who get minor-league forward Daniel Carcillo and a late-round draft pick.
The 40-year-old Roberts, an unrestricted free agent July 1, had hoped to be dealt to Ottawa or his home city of Toronto but in the end accepted the move to join the Penguins after deliberating all day Monday.
Roberts had 13 goals and 16 assists in 50 games with the Panthers this season. In his 19-year career, he has 421 goals and 451 assists in 1,127 games with Calgary, Carolina, Toronto and Florida.
Welch, 24, had split his time this season between the NHL and the AHL. In 22 games with the Penguins, he had one goal and one assist.
Laracque, 30, a native of Montreal who like Roberts waived a no-trade provision, will provide some much-needed protection for young stars Sidney Crosby, Evgeni Malkin and Jordan Staal.
Laraque spent seven years with the Edmonton Oilers before becoming a free agent and signing with Phoenix last summer. He has been forced to take a lesser role with the Coyotes this season. He was a healthy scratch for a game against the Flames last week. He expects to be busier in Pittsburgh.
"I won't be the bodyguard of only one guy and I know that," he said. "I'm going to have look after pretty much the entire team."
He's under contract for US$1.1 million this season and $1.3 million next year.
In 56 games this season, he's recorded five goals and 17 assists with 52 penalty minutes.
Laracque played for Penguins coach Michel Therrien when the Granby Predateurs won the Memorial Cup in 1996.
Carcillo has 21 goals and nine assists in 52 games this season with the AHL's Wilkes-Barre/Scranton Penguins.
To make room, the Penguins traded fourth-line forward Dominic Moore to the Minnesota Wild for a third-round draft pick in June.