Doncaster slipped to the foot of the npower Championship despite a second-half equaliser from substitute Chris Brown.
Rovers were staring at a fourth straight defeat after Jermaine Easter's first goal since Christmas put Crystal Palace ahead.
But Brown, who has missed most of the season through injury, swept in a leveller for the strugglers just four minutes after coming on.
However, a point was far from ideal for either side as Portsmouth climbed above Rovers at the bottom while Palace's already slim play-off hopes suffered another dent.
Yet Dean Saunders' side did not start like the team floundering at the wrong end of the table and should have buried at least one of three early chances.
In the third minute Frederic Piquionne crossed from the left but Fabien Robert's shot was too close to Eagles keeper Julian Speroni.
Unfortunately for Rovers, Piquionne then began to show why West Ham were happy to let him leave on loan in January.
After a quarter of an hour the French striker had a free header from Simon Gillett's cross, six yards out in front of goal, but put his effort woefully wide.
Moments later Robert fed Piquionne in the Palace area but this time he could only prod the ball onto the foot of Speroni's right-hand post.
Palace's cause was not helped by losing two centre-halves to injury in the opening 25 minutes, with Paul McShane and then his replacement, Anthony Gardner, both limping out of the action.
Rovers full-back Pascal Chimbonda was also forced off in the first half, while Palace's enforced reshuffle actually perked them up and they almost took the lead before the interval.
Wilfried Zaha, just back from a three-match ban, tore down the left and his low cross found substitute Glenn Murray, whose first-time shot forced a fine point-blank save from Rovers keeper Carl Ikeme.
And Palace took the 12 minutes after the break, with Zaha the architect.
The teenage winger tricked his way to the left byline and drilled the ball across to leave Easter with a tap-in at the near post.
It could have been two moments later but Murray headed Chris Martin's corner into the side-netting at the far post.
However, Rovers sent on Brown and the former Sunderland trainee made an immediate impact on only his second appearance since August.
In the 76th minute El-Hadji Diouf's cross was only half-cleared by Nathaniel Clyne, Piquionne headed the ball back into the mix and, while Paddy McCarthy dithered, Brown crashed the ball in from close range.
Crystal Palace Speroni, Clyne, McCarthy, McShane (Gardner 6), Moxey, Zaha, Williams (Ambrose 80), Dikgacoi, O'Keefe, Easter, Martin, Gardner (Murray 24).
Subs Not Used: Price, Pedroza.
Goals: Easter 57.
Doncaster Ikeme, Chimbonda (Friend 36), Beye, Lockwood, Ilunga, Robert (Barnes 72), Gillett, Keegan (Brown 73), Oster, Diouf, Piquionne.
Subs Not Used: Bennett, Coppinger.
Booked: Oster, Brown, Ilunga, Friend.
Goals: Brown 76.
Att: 13, 401
Ref: Darren Deadman (Cambridgeshire).