The patched up visitors went ahead early in the game through Dan Gardner’s own goal but Ethan Galbraith’s excellent strike from distance earned Rovers a share of the spoils.
Cambridge, who have now not won in seven games, failed to register a single shot on target.
Doncaster remain 23rd in the table, still three points from safety.
Bonner said: “We’ve come into a game tonight with a mixed and matched side. Jack Iredale going and playing in central midfield, Ben Worman making his first league start, a few of the boys playing their first game for a while, a new goalkeeper having to build a relationship.
“Players like Dunks (Harrison Dunk) and Jibs (Jubril Okedina) haven’t played for about six games, and a lot of players out.
“I don’t think I’ve ever made that many changes from one league game to the next in 18 months.
“It’s slightly frustrating, because when you’re one up and you know you’re going to spend a long time without the ball, but the goal wasn’t under huge threat, and it took a really good goal to get them back in the game.
“On the weight of pressure they potentially deserved that, but it’s hard for us to go and engage higher up the pitch and press – a little bit because of legs, and a little bit of the way in which they moved the ball, and how big they make the pitch.
"It was a tough night for us, I think they’re a good side, they’re in a false position, they play well, and they’re turning a good run of form in, and they’ve had some good results here.
“All in all, the lads are disappointed, because they want to hold on and get the three points, and they know that we need some.
“We need a few wins on the board, but I told them yesterday, if they give us x, y and z, I’d be delighted whatever the outcome, and I am tonight.”