Nathaniel Mendez-Laing had put Dale ahead with a fine curling strike just before the hour mark, but Paul Anderson’s goal in the final minute of stoppage time rescued a point for the visitors at the death.
Joe Rafferty and Steven Davies returned to the starting eleven, replacing Joe Bunney and the suspended Keith Keane.
Although the first half lacked a great deal of tempo, it was Dale who looked the most threatening of the two sides, creating a number of half chances without forcing Northampton goalkeeper Adam Smith into action.
Rafferty sent a left foot effort just over the crossbar with curling effort from the edge of the area, before Ian Henderson and Davies headed off target via crosses from Calvin Andrew and Rafferty respectively.
Henderson then crossed dangerously forcing an acrobatic clearance inside the six yard box, an intervention which came straight back to the Dale skipper, only for him to volley his second attempt well over.
The visitors’ solitary effort of the opening period came from former Dale loanee Marc Richards, who turned Aaron Phillips’ cross from the right well wide.
Nathaniel Mendez-Laing cut onto his left foot and struck just wide of the far post from 20 yards out, before his out-swinging corner was headed over by Matthew Lund who felt he should have done better.
Jamie Allen had the final chance of a quiet opening period, sending a looping header over Henderson’s right wing cross.
Henderson and Allen both had efforts from range after the break, but it was Mendez-Laing who opened the scoring in fine fashion in the 58th minute.
Henderson rolled the ball back to him, and he curled a fine effort beyond Smith and just inside the far post.
It was no more than Dale deserved after creating the majority of the chances so far, although the visitors responded well as they enjoyed their best spell of the game in search of an equaliser.
Paul Anderson curled a left foot effort just wide of Conrad Logan’s right post, before he rattled that same post minutes later.
Substitute Brendan Moloney’s cross from the right was deep to the far post, where Anderson ran onto the ball and headed against the upright from close range.
Callum Camps was replaced by Ollie Rathbone with fifteen minutes remaining, just as Dale required fresh legs in midfield.
Henderson fired wide of the near post after he impeccably brought down a long ball forward, but it would be a long ball forward from the visitors that would be Dale’s undoing in the final minute of three added on.
Anderson was the man to run on to it for the Cobblers, and as Logan came out to narrow the angle, he lifted the ball over the goalkeeper and into the back of the net despite the sliding Dale defenders to steal a point at the death.