Warnock has been linked with a move to Queens Park Rangers and his team played like a side that felt sorry for themselves at the start.
Doncaster gave them the run around in the first half and should have been three or four goals up at the interval.
But they had to make do with a 37th-minute thunderbolt from James Coppinger after failing to make the most of a series of chances.
Rovers dominated the first period and peppered the Palace goal largely without success.
Billy Sharp headed a cross from Coppinger wide in the fourth minute and James Hayter fired a fierce low shot which was saved at the near post by Julian Speroni soon after.
The one-way traffic continued with Doncaster twice getting the ball in the net only to have both efforts disallowed before Coppinger fired them in front in the 37th minute.
The diminutive winger latched onto a short pass before lashing home a left-foot shot into the roof of the net from just inside the box.
Alan Lee and Kieran Djilali both had efforts cleared off the line as Palace tried to hit back but they were fortunate not to go further behind when Speroni made a fine save to deny Sharp early in the second half.
Doncaster sat back after that giving Palace all the encouragement they needed and they were punished by an equaliser in the 67th minute.
Darren Ambrose raced through on the left and turned defender James O'Connor inside out before crossing to the far post where Djilali fired home unchallenged.
Doncaster rallied but left their effort too late although Palace were fortunate not to concede a penalty when Matt Lawrence brought down substitute Jordon Mutch deep into stoppage time.