With a 1-0 advantage going into the second leg Rotherham dominated, striker Adam Le Fondre hitting the crossbar with an inventive chip early on.
And it was Le Fondre who opened the scoring, heading in from point-blank range after Ian Sharps had hit the bar.
A fine move led to Kevin Ellison securing the Millers' place in the final when he headed in the second.
Le Fondre's 88th minute goal in the first leg had stolen Rotherham an advantage going into the return leg and it was an edge the home side never looked likely to relinquish.
On a surface covered in bobbles and divots the first half lacked quality with both sides looking edgy in the opening exchanges.
Against a side which finished one place and one point behind them in League Two, it was the Millers who dominated play with strikers Ryan Taylor and Le Fondre looking dangerous, particularly on the counter attack.
But it was Aldershot who had the first real opportunity on goal when Dean Morgan was given acres of space just inside the area but the striker blazed over the bar after being put through.
That was the wake-up call Ronnie Moore's side needed as, in a warning to what was to come later, Nicky Law found Ellison on the back post but the midfielder put his header over the bar on this occasion.
Le Fondre proved a constant thorn in Aldershot's side and he was unlucky not to give his side the lead with an exquisite, opportunist chip from the by-line which clipped the top of the crossbar.
But minutes later the first attempt on target by either side produced the opening goal.
With two minutes to go before half-time defender Sharps met a deep cross and clattered his header against the bar before seeing it fall to Le Fondre who headed in his 30th goal of the season to double Rotherham's overall advantage.
After being knocked out at the semi-final stage in each of their last two excursions into the play-offs in 1988 and 1999, this time it looked like it would be Rotherham's night.
And again the second half lacked much in the way of goal-mouth action, which suited the home side.
A moment of class from Taylor produced a chance out of nothing when he flicked the ball over his shoulder and used his pace to burst towards the edge of the box but his low drive was saved comfortably.
But after 67 minutes Rotherham finally secured their place in the Wembley showpiece - and they did it in some style.
Ellison's chip was flicked on by Le Fondre on the edge of the area and his headed ball found Law on the right-hand side of the box.
Law chipped an inch-perfect ball to the back post where Ellison had continued his run and the midfielder drove his header into the turf and beyond goalkeeper Mikhael Jaimez-Ruiz to put the Millers into their first play-off final.
Rotherham will face the winner of Thursday night's second leg between Dagenham and Redbridge and Morecambe, a tie which Dagenham lead 6-0 after the first leg.
*BBC Sport
Source: BBC Sport