Goals from Richard Wood and Will Vaulks sent Rotherham to the League One play-off final with a 4-2 aggregate win over Scunthorpe.
With Wednesday night's tie finely balanced after a 2-2 draw at Glanford Park in the first leg, Scunthorpe had the better of the early chances, but once Rotherham grew into the game, they took full control.
Wood's firm header from Vaulks' long throw put them in the driving seat in first-half stoppage time, and provider turned scorer after the break when Vaulks intercepted Ryan Yates' clearance and fired home.
Scunthorpe rallied and Duane Holmes forced Marek Rodak into a full-length save, but once Rory McArdle was sent off for a second bookable offence with 13 minutes to go, the writing was on the wall for the Iron.
Scunthorpe enjoyed plenty of opportunities to break against their hosts early on but had only a timid penalty appeal against Wood to show for it, and Rodak's simple save from Hakeeb Adelakun following a decent counter-attack.
Rotherham grew into the game, first testing young Rory Watson - in only his ninth game for the club - through Michael Ihiekwe, when his header from four yards was kept out by a brilliant reflex save.
And he was at it again to keep out Ryan Williams' curling drive minutes later. But just as Watson's heroics looked to have sent Scunthorpe in level, Wood rose highest to head in Vaulks' long throw in the second minute of added time.
After the break, Scunthorpe again began strongly but failed to take their chances, even when a rare mistake from Rodak gave Ivan Toney the chance to shoot at a goalkeeper-free net, only to see his shot blocked.
And Rotherham doubled their lead on the night, and on aggregate, when Joe Newell's cross was cleared straight to Vaulks by Yates, and he fired beyond a helpless Watson from close-range.
Things went from bad to worse for Scunthorpe, who moments after being denied a comeback goal when Rodak dived at the feet of Holmes, were reduced to 10 men when McArdle was beaten to the ball by Williams and caught him, earning a second yellow.
Rotherham had two late chances to add to their lead through Newell, but the Millers fans were lining the pitch long before the full-time whistle in the knowledge they would be heading to Wembley to face Shrewsbury in the play-off final a week on Sunday.