Burton could have been ahead inside 45 seconds but debutant Garyn Preen drove his shot too close to goalkeeper Jamie Annerson after the hosts broke quickly from a Rotherham corner.
With both teams resting key players, the first half was a scrappy affair until chances fell to Burton’s Greg Pearson after the half-hour mark. But the striker fired too high from the edge of the area before having a low shot pushed round a post by Annerson.
Rotherham had appeals for a penalty brushed aside three minutes after the break when Kevin Ellison claimed he had been tripped as he tried to pounce on a mistake by full-back Andy Corbett.
Rotherham’s improving form was rewarded when Mark Bradley gave them the lead with a superb 22-yard strike in the 65th minute and Ellison added their second from the penalty spot in the 78th minute after being tripped by Corbett.
Substitute Richard Walker reduced the deficit with a close-range finish in the 83rd minute, but the Millers held on.