Goals in each half from Mark Bradley and Lee Frecklington kept the Millers firmly on course for a play-off spot and condemned Oldham to a third consecutive home defeat.
Evans said afterwards: "It was a comfortable win and a fair reflection might have been 8-2.
"It should have been done and dusted by half-time so we had to stay professional and keep passing, which we did outstandingly well.
"We knew it would be tough because Oldham were nip and tuck with Preston here on Saturday, but we did all you could ask.
"We were dominant and our midfield four were great. Once the second goal went in, it was a case of whether we could score three or four. When we play with that sort of application, we are a joy to watch.
"We've got a monster game against Walsall on Saturday and if we win that it might just tell one or two people we can get promoted.
"People expect us to fail, but we are right in there."
Source PA