Kevin Lisbie struck after 22 and 61 minutes before Rovers defender Ian Goodison saw red for striking the Orient forward in the face. With Lisbie receiving treatment David Mooney assumed responsibility from the penalty spot but his kick struck a post.
However, it mattered little as Dean Cox and Shaun Batt wrapped up the win.
Lisbie opened the scoring after Lloyd James waltzed into the penalty area before cutting the ball back for the inform striker to volley in his 10 goal of the season.
Lisbie doubled his tally when his nonchalant flick diverted Cox's miss-hit shot into the top corner of the net.
Goodison got his marching orders for pushing Lisbie to the ground before Mooney struck the post with the resulting penalty which rebounded against his leg and looped into the net, with the referee immediately chalking off the goal as no other player had touched the ball after Mooney's original strike.
Cox stroked in Orient's third goal from the edge of the box after 78 minutes before substitute Batt sealed the win five minutes from time.