Dale were beaten by rock-bottom Torquay in their last away match but they suffered no such slip at second-bottom Northampton as goals from Ian Henderson and Matthew Lund at the start of either half left them in control.
Lund was dismissed immediately after netting his goal, the midfielder picking up a second yellow card for his celebration, but the 10 men of Rochdale were still able to add a third goal thanks to Joe Bunney.
The victory sees Rochdale go a point clear at the summit after Chesterfield slumped to a 2-1 defeat at Plymouth, who move into the play-off places.
Reuben Reid struck both goals for Plymouth, opening the scoring in the 28th minute and then restoring his side's lead just moments after Ritchie Humphreys' 57th-minute equaliser for Chesterfield.
Northampton's loss defeat allowed Torquay to move to within two points of their relegation rivals with their 2-1 home win over Bury.
Torquay looked set to have to settle for a point when Clive Platt's 66th-minute goal cancelled out Lee Mansell's early opener for the hosts, but the Gulls snatched the victory thanks to substitute Ashley Yeoman's stoppage-time winner.
Accrington, who started the day in the bottom three, also boosted their hopes of avoiding the drop as they thrashed local rivals Morecambe 5-1.
Lee Molyneux scored first and last for Accrington, netting in the fifth and 90th minutes, and in between Kal Naismith (penalty), Dean Winnard and Tom Aldred were also on the scoresheet for the hosts.
Morecambe's sole reply came from Padraig Amond when they were 4-0 down.
Also on Tuesday, a 79th-minute penalty from Dean Morgan earned Wycombe a 1-1 draw at Cheltenham, who had taken a 68th-minute lead through Byron Harrison.
- Sports & Recreation
- Matthew Lund