The Millers totally dominated the first half, but couldn't find a way past Jack Butland in the Cheltenham goal.
After Alan Bennett fouled Lewis Grabban in the box with 29 minutes gone, the striker picked himself up to take the penalty but Butland kept it out.
Jason Taylor shot just inches wide and when Butland was beaten by Cresswell's excellent cross there was no-one to turn the ball into the empty net.
In contrast, all Rhys Taylor in the Rotherham goal had to deal with in the first half was the occasional backpass as Cheltenham failed to muster a single shot on target.
The Robins were a little more adventurous after the break and Kaid Mohamed headed just wide before substitute Josh Low put their best chance high over the bar after 63 minutes.
Just as the game looked to be heading for a draw, Cresswell rose highest to power in Ben Pringle's corner to keep the Millers faint play-off hopes alive.
Source: PA