Goals in each half by captain Graeme Lee and striker Danny Cadamarteri mean Brighton have lost nine and won only five of their 21 matches at Withdean this season.
Rovers could have been forgiven for suffering a hangover following their extra-time triumph in the Johnstone's Paint Trophy final against Bristol Rovers in Cardiff last weekend.
But Cadamarteri, on loan from Leicester, and the prolific Paul Heffernan gave the Brighton defence all sorts of problems from the start.
Keeper Scott Flinders denied Cadamarteri twice early on before Rovers took a deserved lead in the 28th minute.
Lee headed their winner from a corner against Bristol Rovers and he struck in similar fashion again.
A corner by James O'Connor was played back to Brian Stock to cross for the unmarked Lee to convert with a downward header.
Brighton's hopes of a second-half revival were dashed two minutes into the restart when a delightful through ball from Heffernan was clipped past the advancing Flinders by Cadamarteri.
Doncaster's first league success since winning at Nottingham Forest could have been even more comprehensive.
Lewis Guy hit the top of the bar with a cross which turned into a shot and Flinders foiled both substitute James Coppinger and Sean Thornton in the closing stages.
Brighton offered little as an attacking threat as they failed to score for the sixth time in their last eight home matches.
The closest they came was when substitute Tommy Fraser miscued a volley on to the roof of the net with a minute left.
Rovers could have been forgiven for suffering a hangover following their extra-time triumph in the Johnstone's Paint Trophy final against Bristol Rovers in Cardiff last weekend.
But Cadamarteri, on loan from Leicester, and the prolific Paul Heffernan gave the Brighton defence all sorts of problems from the start.
Keeper Scott Flinders denied Cadamarteri twice early on before Rovers took a deserved lead in the 28th minute.
Lee headed their winner from a corner against Bristol Rovers and he struck in similar fashion again.
A corner by James O'Connor was played back to Brian Stock to cross for the unmarked Lee to convert with a downward header.
Brighton's hopes of a second-half revival were dashed two minutes into the restart when a delightful through ball from Heffernan was clipped past the advancing Flinders by Cadamarteri.
Doncaster's first league success since winning at Nottingham Forest could have been even more comprehensive.
Lewis Guy hit the top of the bar with a cross which turned into a shot and Flinders foiled both substitute James Coppinger and Sean Thornton in the closing stages.
Brighton offered little as an attacking threat as they failed to score for the sixth time in their last eight home matches.
The closest they came was when substitute Tommy Fraser miscued a volley on to the roof of the net with a minute left.