Keeper's relief as Millers return to winning ways
Warrington said: "It was a massive relief after the losses we have had.
"Performances have been OK recently without getting the results.
"We set about the game at a high tempo. I thought it was a better performance but it's not about that at this stage of the season. It's about results."
The win moved Rotherham back up to fourth spot in League Two and in with a decent chance of making the end-of-season play-offs, but it did come at a cost.
Danny Harrison received a straight red card in the second half and will now miss three matches.
In a bad-tempered game, Craig Hinton and Luke Guttridge were sent off for Northampton, who also saw Ryan Gilligan have a first-half penalty saved by Warrington.
The Millers remain six points shy of the third and final automatic promotion spot with four games remaining.
Lowly Cheltenham are the visitors to Don Valley on Saturday.