The visitors’ direct, no-nonsense style caused the high-flying Millers all sorts of problems and they enjoyed the best of the first-half chances.
Stacy Long should have opened the scoring after 19 minutes when he had only the keeper to beat from 10 yards out, but Andy Warrington somehow blocked with his legs. Then Warrington saved at the second attempt from Michael Bostwick, grabbing the ball just before it spun over the line, while Long saw a free header flash wide.
Rotherham had created virtually nothing, but in the third minute of first half added time the visitors were made to pay for their misses. A free-kick into the box was headed clear to Adam Le Fondre and he picked out Nicky Law, who raced into the box to crash a shot past Chris Day.
Twice more Warrington came to Rotherham’s rescue with saves from Bostwick and Peter Winn before Rotherham thought they had the vital second goal, but Nick Fenton’s header from Kevin Ellison’s corner was ruled out for a push.
And minutes later Stevenage scrambled an equaliser as after Winn’s first shot was blocked, Rotherham could not clear the loose ball and it was tucked away from close range by John Mousinho with eight minutes to go.