The O's looked to be on their way to a priceless win after Gary Alexander put them ahead on 36 minutes before Doncaster came storming back in the second half and could easily have gone on to win the game.
But it was Orient who dominated the opening stages as they created a catalogue of chances.
With Shane Tudor threatening down the right, he set up an early chance for Luke Guttridge, who slid an effort wide from eight yards.
Ryan Jarvis had a shot blocked and skipper John Mackie, a close-range header saved by Neil Sullivan in the visitors goal, before Rovers went close to grabbing a shock lead.
Brian Stock hammered a shot against the post from distance with keeper Glyn Garner scurrying across his goal.
But Orient came storming back and Wayne Corden flashed a free-kick inches wide, before Alexander tested Sullivan.
So it came as no surprise when Orient took a deserved lead in the 36th minute, when Corden's rightwing corner wasn't cleared and Alexander swept home his 11th goal of the season.
But the complexion of the game changed dramatically in the second half as Paul Green rattled the woodwork within 60 seconds of the re-start and then Garner made a spectacular save from Rovers substitute Lewis Guy.
As the pressure mounted, Orient failed to clear Stock's corner and Lockwood rifled home a leveller from eight yards.
After that the visitors could easily have won the game as Bruce Dyer missed a hat-trick of chances and Danny Cadamarteri also almost scored.