Rotherham made it four games unbeaten and stayed ahead of visitors Shrewsbury following a fortunate 1-1 draw in League Two on Monday.
The Millers took the lead through Adam Le Fondre's penalty after 10 minutes at the Don Valley Stadium, but they should have been in front before that.
After five minutes, David Button saved well from Tom Pope and the Shrewsbury goal lived a charmed life as they cleared three follow up shots off the line.
But five minutes later, Le Fondre tempted Graham Couglan into a challenge in the area and the hosts top scorer picked himself up to slot his spot-kick past Button.
At the other end, Jake Robinson twice went close for the visitors in the space of a minute before Dave Hibbert brought a good save out of Andy Warrington with the half drawing to a close.
With a minute of the first half left, the visitors were back on level terms. Warrington could not hold Paul Murray's shot and Steve Leslie drilled the loose ball into the empty net.
Shrewsbury really turned up the heat after the break. Ian Sharps got in a great block to deny Hibbert and then Warrington made two brilliant saves to deny Leslie and Hibbert.