The visitors hung on, though, and took the lead against the run of play when Rochina unleashed an unstoppable effort from 22 yards that flew past Ben Amos in the United goal. But while the strike was out of the top drawer, Rochina will have been surprised by the amount of space he was afforded in the final third.
Rafael hit the base of the post less than 60 seconds after the restart with a smart volley but it was as close as the Reds came to drawing level before Blackburn struck again just on the half-hour. Rochina nabbed his second with a strong finish into the roof of the net from 12 yards after a smart backheel from Michael Potts had played in the Spaniard.
Neither side fashioned a further chance in the first period and the Reds made a double change at the start of the second. Rafael made way for Davide Petrucci, while Nicky Ajose replaced Oliver Norwood.
That prompted a switch in formation, too, as United went from 4-5-1 to a loose 4-3-3, with Ajose flanked by King and Obertan. It almost paid immediate dividends when Bunn spilled a stinging Petrucci shot before doing well to block Ajose's close-range rebound.
The game then threatened to boil over when Robbie Brady and Reece Brown were booked in quick succession for full-blooded challenges (Brown's ended Rochina's involvement in the game), but referee Dean Mohareb did well to diffuse the situation.
United continued to probe for a way back into the game and were duly rewarded on 65 minutes when King's driving run was halted inside the penalty area. Substitue Petrucci stepped up to tuck away the spot-kick and reduce the arrears.