Adam Le Fondre was the difference between the teams, but in truth it could have been game over at the halfway point as the Millers controlled proceedings early on.
Tom Newey had the first effort on goal after five minutes but his shot flew over Tommy Lee's crossbar from range.
Le Fondre then took centre stage as his partnership with the fit again Tom Pope began to look dangerous.
Alf almost had an opportunity on 12 minutes but Dwayne Mattis blocked, and just a few minutes later he hit a crisp volley which angled over the bar after he was picked out by Nicky Law's crossfield pass.
Danny Harrison then missed a golden chance to net the first goal of the afternoon as he somehow headed wide from Kevin Ellison's cross.
As Le Fondre shot wide from Pope's neat knock down, Lee was at his best to parry Jason Taylor's drive as Alf just failed to reach the rebound before the Spireites stopper.
And just before the break Pope's fierce shot was parried by Lee to his left as the Millers dominated.
Chesterfield hit back after the interval though with some sustained pressure late on, as the Millers countered on the break, led by Ellison and Pope's work ethic.
Craig Davies fired over the top for the visitors before the only goal of the afternoon. Le Fondre found a yard of space from Johnny Mullins' throw and expertly clipped the ball over Lee into the corner from the edge of the box to give Rotherham a more than deserved lead.
Warrington then had to be at his best just moments after as he tipped away Dean Morgan's drive as the Spireites countered.
After a barrage of pressure, Warrington again earned his wage with a double save from Derek Niven and Davies' rebound whilst at the other end Ellison was wasteful with a cross straight into Lee's arms.
Pope's hard working display was capped as he kept the ball in the corner to good effect and ran down the clock in an electric atmosphere in the latter stages as the ref brought the game to a close to loud cheers from the home faithful.
Stats to follow later.