There was little to cheer for either side in a disappointing first half. Rotherham struggled to find a way through a packed Rovers defence as the visitors frequently pulled ten men back behind the ball.
When Rovers did break out, Mustapha Carayol usually led the charge, but there was no-one to turn in his excellent cross after ten minutes and then Chris Zebroski fired Carayol's cross into the side netting.
Rotherham had to wait until the 30th minute for a clear chance, but Alex Revell's first touch let him down and he shot over
Four minutes later Sam Wood just failed to reach Lewis Grabban's cross from the left and in first half added time Grabban's goal bound shot was deflected for a corner.
Rotherham should have broken the deadlock four minutes after the break when Revell's first-time ball over the top found Grabban and he raced into the penalty area but steered his shot wide of Scott Bevan and wide of the upright.
And Rotherham spurned another golden chance after 70 minutes when Bevan could only parry Grabban's shot but Revell fired the lose ball over the bar.
And Dorman's injury time winner came when he lashed home substitute Eliot Richards' cross.
Source: PA