Evans is new Millers boss
This season Crawley sit in fourth place in League Two, just two points away from the automatic promotion places.
He replaces Andy Scott who was sacked last month after less than a year at the helm of the Millers.
Evans said he believes he can take Rotherham into the Championship whereas it would be difficult for Crawley Town to get any higher than League One.
Last season he led Crawley to promotion into the football league for the first time in their history, winning the Conference title with a record 105 points after being in charge at the club for four years.
He said: “You only have to look at the vision of the chairman and the vision of the board to see where they want to take the football club.”
“If it wasn’t for that, then I wouldn’t be here. I’m ambitious myself and I’m really looking forward to it.”
The 49-year-old Scot has signed a three-year deal with the Millers.