John Ward's League Two strugglers pulled off a shock by coming from behind with two goals in the final seven minutes to beat their League One hosts in their rescheduled second-round tie.
The original match at the Broadfield Stadium on December 18 was called off after 75 minutes with the scores level due to a waterlogged pitch, but Wednesday's game seemed to be heading the way of Crawley when Jamie Proctor gave them the lead on 15 minutes.
John Gregory's side, who sit 13th in League One, controlled the first half but were unable to find a second goal.
And Rovers made Crawley pay when Eliot Richards appeared to have forced extra-time when he equalised in the 83rd minute, only for O'Toole to then complete the turnaround when he converted the rebound from a Richards effort that was saved by Paul Jones.
Rovers now face a third-round tie at Championship outfit Birmingham City on January 14, with the winners to host Swansea City in the fourth round.
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