The Millers were given a tough test by their European opponents and fell behind midway through the second half after a spell of away pressure.
But the hosts rallied and goals from Matt Derbyshire and Jordan Bowery in the final 10 minutes handed them a come-from-behind 2-1 win.
It ends Rotherham's public pre-season friendlies - they travel to Sunderland for a behind-closed-doors friendly in midweek - and Evans was happy to sign off on a high.
"It was a first half-performance which was more disciplined, worrying more about the shape rather than our offensive play," he said. "We’re still working hard to get the right balance with the group.
"In the second half we’ve had more offensive play. We’ve just looked at the Bundesliga clubs who are playing pre-season games in England.
"One goes up to Newcastle and wins, one wins at Stoke City, one draws with Bournemouth.
"We’ve beaten a team packed with stars if you have knowledge of German football. We had to work really hard and have a good shape and discipline. But there are a lots of things to work on."
Evans gave further clues as to his thinking ahead of next week's Sky Bet Championship opener against MK Dons, with four of his back five looking settled and just the left-back issue to sort.
However, the Scot insists there shouldn't be too much read into the line-up against Mainz.
"That certainly won’t be our team to play MK Dons, but we’ve had a lot of plusses," he added. "We’re going up to Sunderland on Tuesday for a behind-closed-doors match and we’ll get some game time into those who need the minutes.
"Some of them have already ticked that box. You can’t read too much into today’s starting line-up but players always do and supporters always do.
"We have to make sure that, as best we can, we pick who we think can beat MK Dons on Saturday."
