Last season's play-off contenders were seemingly comfortable when Chris Brown, on loan at Rovers six seasons ago, capped Preston's dominant first half with a well-taken strike on 28 minutes.
But Doncaster, whose set-piece repertoires had been studied by Irvine's team, hit back 11 minutes from time following a quickly-taken free kick.
Substitute Dean Shiels whipped in the cross from the left, Jason Shackell had a shot blocked in the scramble and Adam Lockwood prodded an equaliser across a crowded goalline.
It disappointed Irvine, who felt his team "passed Doncaster to death" in the first half, only to fail to put into practice what they had learned in the build-up to the game.
"That was two points lost," he said. "We know Doncaster very well. We know they have players with imagination and ability; we had a video session this morning and showed the lads who are going to take short free kicks and short corners and explained that it was important to be alive to them.
"Unfortunately we had either a lack of concentration or a bit or tiredness and we switched off. That is bitterly disappointing because the work had been done in preparation.
"I thought we passed them to death in the first half.
"We had the lion's share of the ball and we were very comfortable. We put some great crosses in.
"In the second half we passed poorly and made bad decisions. It's just disappointing that we switched off defending a free kick."
Irvine's team had looked the stronger side in an entertaining first half, with Barry Nicholson and Paul Parry both looking dangerous before Brown opened the scoring.
The 24-year-old outran two defenders to collect Ross Wallace's through ball before side-footing a low shot across Neil Sullivan and inside the right-hand post.
It was his second goal in as many games, having also opened the scoring in the 5-1 Carling Cup rout of Morecambe on Tuesday.
But Doncaster hit back with a series of near-misses, the closest of which was a James Hayter close-range drive against a post, while Shiels nearly won the game with a sweetly-hit drive from 25 yards in the final minutes.
Despite Irvine's disappointment, Doncaster manager Sean O'Driscoll felt his side were the better team after the break.
"We kept our discipline and shape after we went a goal down," he said.
"I thought we dominated the second half and for a while I did think it was going to be one of those days again when we wouldn't convert the chances that we created.
"But we got one in the end and I thought we looked the more likely team to go on and win it.
"I try to not to use the word 'unlucky'. We created chances and did not take them. James Hayter will rue the fact he hit the post. Nine times out of 10 he scores and we give ourselves a chance. Every point counts in this division."