Veteran striker Mark Robins produced a stunning equaliser to deny Paul Hart's play-off bound Forest a win.
The former Manchester United star volleyed an exquisite volley a la David Platt in Italia 90 after Chris Sedgwick's flick dropped over his shoulder.
His leveller rounded off a second-half flurry after a low-key first-half stroll in the sun for Forest, assured of a shot at promotion and Ronnie Moore's Rotherham certain of another season in the first.
Rotherham's newly capped Republic of Ireland striker Alan Lee celebrated his call-up by scoring his 15th goal of the season after 54 minutes.
He produced a cool finish placing a smart shot after the best move of the match, a slick build-up involving Stewart Talbot and Robins.
But Forest got in the mood for the play-offs by responding with two goals in three minutes to turn the tables.
Riccardo Scimeca took a quick free-kick and, as Rotherham were still arguing, Jack Lester darted in and levelled with a close-range finish.
It was Scimeca's clever thinking that created the second. He picked out Lester again and when Ian Gray raced out of his area to block, Craig Westcarr was on hand to fire the rebound into the open net.
But it was left to Robins to have the final with his seventh goal of the season for the South Yorkshire side on top of his five on loan at Bristol City.
Rotherham could have been in front in the first half but Forest keeper Barry Roche produced a splendid save seconds before the break.
It came when Sedgwick snapped up a loose ball, cut into the area unchecked and lashed a fierce low shot towards goal. Roche showed great reactions to parry it and the rebound ran away from Robins as he darted in.
And Forest had lived dangerously earlier when Guy Branston was just wide with a towering header when Talbot lifted in a clever cross after Shaun Barker's monster throw-in.
But the game came alight after the break and left both sets of fans celebrating.