A record crowd at the all-seated Nene Park, nearly 5,600, saw the Football Conference's fourth-placed club earn a tilt at Leeds in a replay victory which did scant justice to Doncaster, who played most of the game with 10 men.
The match began disastrously for the Conference's bottom club, already without their injured player-manager, Ian Snodin, and rapidly got worse.
With under three minutes played, their striker Mark Hume, was sent off after a two-footed lunge a la Dennis Wise, on Darren Bradshaw.
The Yorkshire side had scarcely regrouped before Duane Beckett felled Rushden's Carl Heggs inside the penalty area in the sixth minute, and John Hamsher dispatched the spot-kick beyond Andy Woods.
The visitors equalised after 18 minutes. The opportunity was fashioned by one centre-back, when the much-decorated Steve Nicol volleyed into the goalmouth, and accepted clinically by the other, Colin Sutherland, who shot in as Rushden looked for an offside flag.
Rushden dominated in territorial terms but made hard work of asserting their numerical advantage. Although the widely travelled striker Colin West headed wide from close range, they were otherwise restricted to long distance efforts before the interval.
Doncaster's David Penny almost sneaked a free-kick past Mark Gayle in the opening thrust of the second half. However, just when Rushden were starting to run out of ideas they went ahead again in the 63rd minute. Bradshaw's cross was met by a header from West which looped over Woods.
Moments later, Doncaster's frustration spilled over when Sutherland aimed a punch at West in the home penalty area. Neither the referee nor his assistant spotted the offence, but Rushden landed a knock-out blow themselves when Brady headed in a left-wing cross in the 68th minute. West, pouncing on an under-hit back-pass by Nicol, claimed his second goal with six minutes left, before Doncaster's Tunisian substitute, Noureddine Maamria, gave the scoreline a more respectable sheen.
Rushden & Diamonds (4-4-2): Gayle; Wooding, Bradshaw, Warburton, Underwood; Brady, Hamsher, Butterworth, Heggs; West, Collins (Mison, 76). Substitutes not used: Foster, Wilson, Rodwell, McElhatton.
Doncaster Rovers (4-4-2): Woods; Warren, Nicol, Sutherland (George, 87), Maxfield; Goodwin, Penney, Beckett (Duerden, 71), Wright; Hume, Kirkwood (Maamria, 85). Substitutes not used: Cauldwell, Jones.
Referee: S Mathieson (Stockport).