With both sides at the wrong end of the Championship table battling to avoid relegation, Abdoulaye Meite's first-half sending off for the visitors looked like being a pivotal moment.
The Ivorian was given his marching orders for a clumsy challenge on Stefan Maierhofer that referee Fred Graham deemed worthy of a straight red.
But Sam Johnstone in the visitors' goal was in inspired form, the Manchester United loanee making superb saves to deny Shaun Williams and Steve Morison in the second half.
The draw keeps both sides out of the relegation zone, both locked on 44 points, with Birmingham and Blackpool one point further back.
"I'm not disappointed at all, I'm pleased with the performance" said Holloway.
"Funnily enough I thought the referee changed the course of the game. I don't think it was a sending off at all. I thought at most, at worst, it was a yellow card.
"Then the expectation of everyone is that you're up against 10 men. It's easier for them to sit in, have an excuse to sit in. It was just a matter of time until we scored. I still can't really believe that we haven't.
"But that's life. We keep going. We were the better team.
"Well done to them (Doncaster) to show that sort of spirit. I thought they got that from the referee. I think they felt aggrieved and I think they held themselves in and even now I can see that save from Morison.
"Gracious me where did that hand come from? I thought it was in. I was celebrating."
The draw means that Millwall are still searching for their first home win since January while Rovers ended a run of four straight defeats.
And boss Paul Dickov was full of praise for the character shown by his side in holding on for a share of spoils in the face of mounting pressure.
"I'm immensely proud of the players, especially the second-half performance," he said.
"You talk about players putting bodies on the line for the club and for the fans and their team-mates and I had that in abundance in the second half.
"It's not (a red card). I didn't think it at the time, I've seen it numerous times. Ian Holloway for me hit the nail on the head at the time when he said it's debatable whether or not it was a yellow.
"They both went for the ball. I've been told it was six studs in the chest - it was nowhere near his chest.
"In a game of this magnitude it's the wrong decision. I don't want to sound as if I'm moaning about referees all the time but some of the major decisions that went against us are not good enough."