The Millers looked to be heading for another home defeat until Kieran Agard hit home in the 5th minute of injury time to score his second of the game to share the spoils.
Former Rotherham striker Matt Tubbs put the visitors in front. He scored just once in 17 appearances for Rotherham, but was on target in the 23rd minute for his new club, tapping in from close range after Nicky Adams' cross was only parried by home keeper Adam Collin.
Kari Arnason should have given the home side the lead after two minutes when he somehow headed wide from five yards out.
But Rotherham equalised from the penalty spot after 33 minutes. Joe Walsh tripped Ben Pringle just inside the area and Kieran Agard made no mistake for his 14th of the season.
Two minutes before the break on-loan Richie Smallwood almost marked his debut with a goal when he fired just wide with a curling shot from the edge of the penalty area.
But Crawley took the lead for a second time after 65 minutes, and again Tubbs was involved as he played a smart one-two with scorer Josh Simpson, who made no mistake from close range.
But in the fifth minute of added time Rotherham's pressure finally paid off when Agard slammed home his second from close range.