Roy is entering the final year of his contract after underperforming last season for Buffalo. Following season-ending surgery to repair a torn quadriceps tendon in 2010-2011, Roy had 17 goals and 27 assists in 80 games last season. He scored at least 25 goals from 2007-2010 before he was hurt. The 5-foot-9, 184-pound Roy has 161 goals and 266 assists in eight NHL seasons, all with Buffalo.
"We had a hole at the center position. By trading Ribeiro we needed to fill that hole," Stars general manager Joe Nieuwendyk told ESPN.com's Pierre LeBrun. "We're trying to incorporate other kids at forward and this allows them to stay in their right spots. This deal made sense for us."
Ott had 11 goals and 28 assists in 74 games with the Stars last season. The 25th overall pick in the 2000 entry draft, Ott has 85 goals and 135 assists in 566 career games and the Sabres are hoping he can address criticism that the Sabres lack toughness.
Pardy spent one year with Dallas after playing his first three seasons with the Calgary Flames. The 6-foot-4, 217-pound defenseman had three assists in just 36 games last season and has 29 career points.
Information from The Associated Press contributed to this report.