Two goals from teenage striker Chris Brown left Doncaster needing just one point to clinch the Third Division Championship and effectively sentenced York to relegation.
City played like a team already doomed and Rovers raced into the lead with two goals in the first eight minutes.
Gregg Blundell bundled the ball home from close range following superb play by John Doolan and Michael McIndoe in the 5th minute.
York were rocked again three minutes later when Brown fired home in fine style after receiving the final pass from Blundell following another slick move.
Doncaster should have had more goals to show for their dominance but Blundell failed to control the ball with the goal at his mercy after Doolan had created the opening in the 18th minute.
Paul Green dribbled through on the left but Mark Ovendale charged out to smother his shot and then Blundell headed inches wide in the 22nd minute.
It was all too easy for Doncaster with York looking particularly shaky in defence but the home side took their foot off the pedal and visiting player manager Chris Brass sounded a warning when he fired inches wide in the 31st minute, Rovers started the second half the same way they had started the first but this time had no goals to show for their efforts.
Blundell should have scored when he was left unmarked in the 47th minute but headed Green's cross well off target.
York grabbed a goal out of the blue two minutes later when Darren Dunning hammered home a 25-yard free-kick round the defensive wall and into the bottom corner.
It provided the wake up call Doncaster needed and Mulligan hit the bar a minute later before Brown made it 3-1 in the 57th minute.
Tim Ryan and McIndoe created the opening and Brown hammered the ball home giving Ovendale no chance to sentence the visitors to their 18th successive game without a victory.