A fairly low-key evening at the City Ground was sparked into life by Dexter Blackstock and Michail Antonio as they netted on 43 and 45 minutes to stun the Millers and send the Reds into the break with a firm grip on the game.
That was one they did not relinquish after the break to keep a second clean sheet in succession and reduce the gap back to Brentford in the final play-off place to 8 points.
Two points further ahead of the Bees are Norwich City and that is where Forest head to next, full of confidence after a 7th win in 10 games under the management of Dougie Freedman.
20,569 watched the action and also caught a late glimpse of new loan signing Modou Barrow who entered the fray on 79 minutes for Blackstock.