Chances were few and far between in a tight first half, but Blackburn came close early on when Jordan Rhodes headed just wide from Tom Cairney's free kick.
Rotherham appeared happy to operate on the counter-attack for much of the game, and the visiting supporters felt that a break should have resulted in a penalty when Matt Derbyshire's shot appeared to strike Matt Kilgallon's hand.
A fairly uneventful opening 45 minutes looked set to end goalless until Craig Conway broke the deadlock in impressive fashion as he cut in from the left wing to pick out the top corner with a curled effort.
Blackburn were keen to get onto the front foot once again early in the second half, but they wasted a big chance to double the lead when Grant Hanley headed wide after latching on to a free kick from Cairney.
Rotherham refused to sit back, though, and Blackburn were put under pressure for long stages of the second half as both Kilgallon and Hanley were forced into crucial clearances.
There was no chance of either defender making an interception when Rotherham equalised in the 72nd minute through Derbyshire, who timed his run well to convert Paul Green's cross.
Rudy Gestede, who started the game on the bench once again, appeared to waste Blackburn's best chance to find a winner when he struck the post from a promising position.
However, there was time for another twist as Blackburn clinched all three points when Rhodes hammered the ball home after a long ball into the box caused problems for the Rotherham defence.