The Latics were under strong pressure as Doncaster looked to cancel out Leon Clarke's early opener, but Craig Rocastle gave them some breathing space and Chris Taylor bagged two more for himself.
Taylor's first ever senior strike took 51 games, but he has now claimed three in two, the latest giving Oldham a scoreline which was rough on Rovers.
Poor finishing was the big weakness for Rovers, whose inconsistent run is keeping them out of League One's top six.
Oldham went in front after just eight minutes after the Doncaster defence was unable to clear the danger following a cross to the far post.
Skipper Graeme Lee did not realise Clarke was snapping at his heels and the striker, making his home debut after signing on loan from Sheffield Wednesday, got the vital touch for a scrappy goal from six yards.
Clarke was denied three minutes later as keeper Neil Sullivan dived to his right to turn away a low shot from the edge of the box.
Sullivan also kept out Rocastle and Paul Warne as his impressive personal display kept Oldham within touching distance.
Doncaster got on top later in the first half, but they missed two good chances, both from set-pieces, as Lee headed over and his central defensive partner Harry Worley prodded off target.
More openings came for Brian Stock and Mark Wilson, who missed by inches, but Rovers could not make their pressure tell.
They paid for that fact after 74 minutes as Oldham broke forward to score from a throw-in, when Rocastle hit his volley from 14 yards into the ground and beyond the dive of Sullivan.
The game was effectively over within two more minutes as Taylor jumped highest at the far post for a simple header from Andy Liddell's deep cross.
Oldham rounded off their victory in stoppage time when Warne did well down the right and his centre was tapped in by Taylor from six yards.