Tommy Smith's tenth goal of the season looked like it would be enough to settle a dull affair in the home side's favour, but the on-loan Bristol City striker came off the bench to score with virtually his first touch.
Doncaster may have the worst goalscoring record in the division but they nearly took a shock lead when a Richie Wellens' cross-cum-shot from the left was pushed onto the underside of the bar by Scott Loach.
Chances were few and far between though, until the home side took the lead in the 31st minute.
Tamas Priskin did well to win a header in a central position and find Jobi McAnuff, who attacked the heart of the Doncaster defence before sliding the ball to his right where Priskin had found space in the penalty area.
The Hungarian striker resisted the temptation to shoot and instead slid a fine ball across the six-yard box where Smith slid in unmarked.
Apart from seven yellow cards - six of which came in a 18-minute period at the end of the first-half - little of note happened until Doncaster scored only ninth goal of the season with 20 minutes remaining.
John Spicer did well on the right side of the penalty area and Brooker got in between two Watford defenders to slide in the equaliser against his first club.
James Coppinger came the closest to winning it for either side with a 20-yard shot that Loach saved, but there was little else of note except for the yellow card count which ended at ten.