Roy, who missed five games with a groin injury, will be available Monday night at Colorado. Nilstorp and defenseman Jordie Benn have been sent to the Texas Stars of the American Hockey League.
Roy has two assists in four games for Dallas. He came over in an offseason trade with Buffalo. Benn is scoreless with four penalty minutes in eight games for Dallas.
Nilstorp missed four games with a groin injury. He was 0-2 filling in for Lehtonen. Nilstorp appeared in 28 games for the Texas Stars before joining Dallas after the lockout ended.