The Oilers also claimed winger Matt Fraser off waivers from the Bruins on Monday.
Roy has one goal and nine assists in 26 games this season.
In 692 career games, the 31-year-old veteran from Ottawa has 178 goals and 324 assists.
Edmonton adds some size and skill with Fraser, a 6-foot-1, 204-pound winger from Red Deer. The 24-year-old had three goals in 24 games for Boston this season.
Fraser is on a $625,000, one-year contract while Roy is on a one-year, $1 million deal.
Also, the Oilers waived forward Steve Pinizzotto.