The former Leeds frontman, on loan from Fulham, headed home a 75th-minute equaliser after Doncaster had looked the better side for most of the match.
There was little to chose between the teams for the first half hour with City keeper Frank Fielding doing well to save at Dean Furman’s feet before Todd Kane fired straight at Sam Johnstone after bursting clean through at the other end.
But the home side enjoyed a purple patch just before the interval and were unlucky not to take the lead when Paul Keegan had a header cleared off the line before James Coppinger had a goalbound effort deflected wide.
Doncaster snatched a deserved lead in the 50th minute when Luke McCullough lashed the ball home following a corner to notch his first goal for the club.
Smith’s equaliser from a deep cross from Luke Ayling was tough luck on Doncaster, who twice went close to snatching victory in the closing stages through lively substitute Kyle Bennett.