Rovers enjoyed the better of the opening period and took a deserved lead when James Hayter finished clinically from Gareth Roberts' cross.
Neil Mellor tapped home from close range three minutes before the interval to pull Preston level, before Sharp saw his 55th-minute spot-kick saved by Andy Lonergan.
Both sides had further chances in a frantic second half, but neither was able to find a winner.
Rovers remain a point clear of their opponents in the Championship, with both sides seemingly set to do battle in the same division next term.
Paul Coutts returned from suspension to replace Matthew James in the centre of Preston's midfield, while Chris Sedgwick started on the left in place of Ross Wallace.
Centre-half Elliott Ward came in for Sam Hird in the only change to the Doncaster side that romped to a 5-2 victory over Bristol City at the weekend.
Preston started the game brightly, with Jon Parkin testing visiting goalkeeper Neil Sullivan from 12 yards.
However, Doncaster soon took control and Jay Emmanuel-Thomas curled a left-footed shot wide before fellow loanee Ward went close with an acrobatic effort from a corner.
Emmanuel-Thomas threatened again in the 25th minute, but Lonergan made a fine save to keep out his low shot from close range.
Lonergan was then called into action to keep out a header from Hayter before Rovers made a deserved breakthrough in the 28th minute.
Roberts' powerful long-range shot was parried away by Lonergan. But the resulting corner was cleared only as far as Roberts and the full-back's chipped cross found Hayter, who found the bottom corner with a superb left-footed finish on the turn.
Preston defender Youl Mawene made a fine block to deny Hayter a second goal two minutes later as Rovers continued to create chances at will.
But Darren Ferguson's men weathered the storm and got back on level terms in the 42nd minute.
Sean St Ledger earned a free-kick when his powerful run was ended in cynical fashion by Chambers, who was handed a yellow card. Coutts' inswinging delivery from the left found Mawene at the far post and he slid the ball across for Mellor, who had the simplest of tap-ins from barely a yard out.
Doncaster were given a golden chance to retake the lead when they were awarded a penalty 10 minutes into the second half.
Chambers went down in the area under pressure from St Ledger but Lonergan dived to his right to keep out Sharp's spot-kick.
Mellor curled a shot narrowly wide shortly after the hour mark as Preston looked to capitalise on their let-off.
Chambers then had a lucky break of his own as he somehow avoided a second booking for a trip on Coutts.
With play switching quickly from end to end, Mellor shot tamely at Sullivan from 18 yards and Sharp fired over for Doncaster from an acute angle.
Sharp went even closer in the 71st minute as he dragged a right-footed shot inches wide of Lonergan's right-hand post.
At the other end Sullivan pulled off a fine save to deny Parkin after the burly forward had turned his marker with ease inside the area.
The hosts had one further chance with a minute of normal time remaining as substitute James burst into the area, but his shot was comfortably pouched by Sullivan.
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