The Icelandic international midfielder was shown a straight red five minutes before time when he challenged for the ball with Rovers midfielder Robbie Savage.
Referee Chris Foy sent Einarsson off but not Savage and Blackwell says he got it wrong.
"Robbie Savage also jumped in and they've both gone for the ball," he said on the official Leeds website.
"I've seen the video and the ball's there and they've both gone for it with feet off the ground but Robbie wasn't injured, he's got up afterwards and waved to the Leeds fans.
"We'll look at the video again before deciding whether we will appeal, but if he's sent Gylfi off then he's got to send Robbie off.
"Neither of them should have gone because the evidence is that both of them left the floor and went for the ball, none of them went above the ball, both of them went for the ball. The referee was wrong."
Blackwell admitted the club are unlikely to appeal against the decision, which means Einarsson will miss the next three games, leaving the Whites depleted in midfield.