However, under Sean O'Driscoll, Sharp has rediscovered the form that saw him rise to prominence at the Iron and he scored for the sixth straight league game and the 11th time this season after 21 largely uneventful minutes at Pride Park on Saturday.
Paul Green had shot wide for Derby early on and Rams goalkeeper Stephen Bywater fumbled a 20-yard shot from Sharp after 15 minutes before Sharp opened the scoring.
After Robbie Savage had lost possession in the middle of the park, John Oster ran goalwards down the right-hand side and set up Sharp, who converted from six yards out.
DJ Campbell, making his first home start since joining Derby on loan from Leicester just over three weeks ago, worked Rovers keeper Neil Sullivan with a shot from the edge of the box five minutes afterwards.
At the other end, Oster missed the target with an effort from a similar distance on the half-hour mark before Bywater had to tip Mark Wilson's volley over the crossbar just before the break.
Derby looked like they might make more of a fight of it when Stephen Pearson was denied by a blocking challenge from James O'Connor five minutes after the restart.
Substitute Rob Hulse, introduced after 56 minutes along with Chris Porter at the expense of Campbell and the Rams' other Leicester loanee Paul Dickov, then headed a good chance over the crossbar just before the hour mark.
Sensing that the hosts were close to halving their deficit, Doncaster boss O'Driscoll opted to protect his side's lead by bringing on defender Sam Hird and taking off striker Dean Shiels.
And aside from a couple of scares from close-range headers from Porter and Pearson midway through the second half, his plan worked perfectly.
Derby manager Nigel Clough replaced Savage with the more attack-minded Lee Croft but it was Doncaster who continued to create chances.
Oster dragged a shot wide and Sharp shot straight at Bywater inside the final 15 minutes.
James Coppinger then capitalised on a lack of concentration in the Rams defence four minutes into stoppage time to beat Bywater with a low shot from 12 yards with almost the final kick of the game.