The Millers’ 14 game unbeaten run was ended as Stephen Humphrys struck the game’s only goal.
Rotherham’s Marek Rodak made the first save of the game as he rushed out to deny Andrew Cannon.
The visitors threatened again through Humphrys but his shot was diverted wide of goal.
Rotherham thought they would have a half-time lead but Richard Wood’s header was disallowed for a foul on Josh Lillis.
Rochdale’s Brad Inman was denied early in the second half by another good stop from Rodak after bursting clear of the defence.
The away side deservedly went ahead after 67 minutes when Humphrys lashed a shot into the bottom corner following a rapid build-up.
Joe Mattock denied Ian Henderson a good chance for a second with a well-timed tackle in the box.
Semi Ajayi’s late effort for Rotherham was cleared off the line and Rochdale hung on for back-to-back league victories.
Rangers manager Steven Gerrard is weighing up a move for Liverpool full-back Jon Flanagan, reports claim.
Scottish champions Celtic are reportedly ready to offer full-back Calvin Miller a new deal before sending him out on loan.
Everton target Jack Wilshere has sparked a scramble for his signature after confirming he is leaving Arsenal this summer.
Tottenham's hopes of landing Wilfried Zaha have been hit by the news Crystal Palace have offered him a bumper new deal to stay.
Ryan Giggs says Gareth Bale would be the perfect fit for Manchester United but has doubts over whether he will leave Real Madrid.
Manchester City's attempts to sign Riyad Mahrez could be in doubt again as reports claim Leicester only want a straight cash deal.