Blackburn were under pressure early on as Ian Henderson pushed for a goal inside the opening 10 minutes, but his shot went out off the outside of the post.
Blackburn were ahead inside the opening 20 minutes as Lee Williamson found the bottom corner with a 20-yard rocket after winning the ball back in midfield moments earlier.
Henderson had a chance to get the hosts back on level terms less than 10 minutes later, diving to head the ball towards the Blackburn net, but David Raya was able to make the save.
The striker did get the better of Raya just after the half-hour mark though, collecting a through-ball from Jamie Allen before calmly slotting past the keeper.
After a quiet start to the second half, it was Rochdale who came closest to finding a second goal when Calvin Andrew came off the bench to head just over the crossbar from a corner.
Blackburn made nine changes with just over 10 minutes to go, and the home side took advantage with a quick break. Reuben Noble-Lazarus was left to find a gap in the visiting side's back four, setting up Henderson for his second of the night and securing the win for the League One side.