Goals from Ricky Shakes and Charlie Comyn-Platt were enough for the Robins to record their third straight home victory and drag David Penney's Doncaster, who scored a consolation through Ross McCormack, into relegation mire.
In the space of just two months Rovers had gone from play-off hopefuls to serious relegation candidates.
It was a limp display from the Yorkshire side who apart from McCormack's goal on the hour mark showed little promise in the final third.
But Penney's problems don't seem to be just going forward as goalkeeper Alan Blayney's fumble on 29 minutes gave the home side the lead.
A corner from Aaron Brown was not held by the Northern Ireland international and when Sean O'Hanlon headed the ball back into the six-yard box, Shakes was left with the easiest of finishes for his first ever goal for the club.
Swindon nearly added to Doncaster's misery on the stroke of half-time when they seemed to have a cast-iron penalty appeal turned down after Anthony Griffiths had handled a Shakes cross.
But they did manage to double their lead on 57 minutes when livewire striker Jamie Cureton outwitted the Doncaster backline with a clever flick to allow Comyn-Platt to blast his second of the season from 12 yards.
McCormack's headed goal a little under 10 minutes later kept the pressure on Swindon and whenever the Yorkshire side got near the home goal nobody in the ground seemed confident of victory.
McCormack spurned a great opportunity on 75 minutes when he raced away from Jerel Ifil only to cut back on to his right foot when strike partner Paul Heffernan was well placed on the far post.
Heffernan then had a shot deflected wide from a corner three minutes later but Swindon's defence held out to record an important victory.