The hosts had a man sent off in the closing stages of the first half when Bobby Grant was dismissed for a reckless challenge on former Dale defender Rory McArdle.
The incident sparked ugly scenes on the touchline with Spotland chief John Coleman and Bantams boss Phil Parkinson involved in a heated exchange.
Coleman had the last laugh as his young defence held the Bantams at bay for 55 minutes to stretch Dale's unbeaten run to five matches.
Parkinson's men created the better chances during the opening 45 minutes, James Hanson's volley and a glancing header from Luke Oliver both held by Josh Lillis in the Rochdale goal.
Bradford skipper Ricky Ravenhill fired a well-struck shot on target in the opening minutes of the second period, but he too was denied by Lillis. Rochdale's young defence coped well under increasing pressure, 18-year-old Joe Rafferty clearing Andrew Davies' effort off the line as the game drew to a close.