Warrington made four point blank stops to keep Rotherham in proceedings after they had started looking like the only team likely on the night.
The Millers opened up the brighter of the two sides and should have taken the lead inside five minutes. Firstly Tom Pope's flick flashed over from Gavin Gunning's left wing cross and then Nicky Law curled a sweet shot left footed just past the angle of post and bar.
Then Pope's half struck effort was blocked by Button, and Adam Le Fondre's low shot was blocked on the line which resulted in a frantic goalmouth scramble as the ball deflected for a corner.
But they did take the lead on 12 minutes as Le Fondre reached 20 league goals for the season, winning then smashing home a penalty after an alledged tug on his shirt by former Rotherham centre back Graham Coughlan.
The Millers could have made it two moments later when a Kevin Ellison shot from 25 yards was saved by Button, then Ian Sharps drove just over from a similar position.
The visitors started to find their feet just after the quarter hour after Rotherham had racked up five shots on target as Jake Robinson picked up Joe Skarz' lay off, but his shot whistled wide of Andy Warrington's upright.
Another former Miller Dave Hibbert began to trouble Sharps in the air, and it was Warrington who denied him with his first super stop of the night, parrying away a point blank volley from Robinson's raking diagonal ball.
However the equaliser, which had been coming, arrived shortly after on 44 minutes as Stephen Leslie pounced to finish off into an empty net after Warrington had pushed aside Paul Murray's drilled shot.
Rotherham offered little after the break and had Warrington to thank again as he produced three more superb stops, firstly on 69 minutes as he blocked debutant Jamie Cureton's effort.
Closely afterwards Hibbert saw another right footed shot blocked by Warrington's legs as he spun in the area and then Leslie's sweet left foot strike, as he beat the offside trap, was pushed over the top by the 'keeper's outstretched hands low to his left.
The Millers introduced Ryan Taylor and Marcus Marshall, but to little effect, as Leslie had the chance to win it deep into injury time for the Shrews but he curled his free kick over the top when it looked more suited to a drive at goal.