Former Millers favourite Deon Burton did the damage with a goal in each half. Rotherham staged a game fightback, had two penalty claims turned down and hit the woodwork, but had to be content with Jason Taylor's 69th minute consolation.
"This was a big game for us," said Evans, "But if this was the benchmark we have shown we can beat that benchmark.
"Some of the stuff that went on in the match I am surprised it remained 11 v 11, as probably do most people in the ground, but if we play like this every week we will win promotion. We were fantastic. A couple of Gillingham's back room team have admitted to me that they rode their luck. That's the biggest understatement I've ever heard."
And Evans hit out at the challenge from Burton that forced home skipper Ian Sharps off injured after 15 minutes.
"It was a nasty, horrible vindictive challenge," Evans said. "It deserved a straight red but the referee missed it. We'll look at the DVD and if its as bad as we think it is I'll send it to the Football League."
Gillingham boss Martin Allen said: "It was a fantastic result and a fantastic performance for us.
"Rotherham are a top form team at the moment and we have gone through a little patch where we haven't turned good performances into results and it has tested our resolve, but we have done the same work.
"Rotherham are a good team and at times it was backs to the wall and our keeper has made a couple of good saves and everyone on our team had to defend defiantly. But then when the chances came at the other end, that partnership of Danny Kedwell and Deon Burton is very, very dangerous so I was delighted with all our squad.
"They were good goals from Deon and he's been a good pro since he joined us and he looks after his body, trains and practices hard and you get those rewards when you do that."