Gary Alexander slid home an 88th minute winner as Martin Ling continued his impressive run as caretaker manager.
Ling has lost just one of seven league games since taking over from Paul Brush but admitted afterwards that the match could have gone either way.
Orient controlled the first half but Rochdale looked the better side after the break and were unlucky to go home empty handed.
Ling said: "This was a massive win for us and that's 14 points from 7 games which is a good return by any standards." Orient started well as skipper Dave McGhee and Alexander went close with headers in the first five minutes before the O's took the lead midway through the half when Matthew Lockwood fired home from the penalty spot after Michael Simpkins was adjudged to have pushed Wayne Purser.
Rochdale boss Alan Buckley growled: "I will see a lot of incidents like that one this weekend but not too many of the them will be given as penalties." Lockwood went close twice more before the break while Rochdale threatened on the counter attack and Orient keeper Lee Harrison saved well from Lee McEvilly's close range header.
After the break the introduction of substitute Patrick McCourt swung the game in Rochdale's favour and the visitors deservedly levelled when McEvilly drilled home a penalty after McCourt's surging run ended when he was pushed over by Dean Hammond.
As Rochdale continued to threaten, Harrison saved well from the ever dangerous Chris Shuker before Orient regained their grip on the game.
In the closing stages Alexander hit the bar with a header before he slid home the winner from Boniek Forbes's cross from the left.
Rochdale boss Buckley reflected: "I think 1-1 would have been just about right we didn't look hungry enough in the first half but for half an hour after half time we played as well as any side in this division."