Doncaster set up a League One play-off final against Leeds on 25 May after a dominant semi-final win over Southend.
James Walker hit the crossbar for the visitors early on and paid for the miss when Brian Stock scored a penalty.
Southend's Adam Barrett headed into his own net and the sublime James Coppinger twice ended mazy runs with precise strikes to put Doncaster 4-0 up.
Coppinger bent in a free-kick for his hat-trick before Nick Bailey netted a consolation for the stunned visitors.
Doncaster had been quick to get out of the blocks but they should have been behind after a swift counter-attack from the visitors after eight minutes.
Simon Francis whipped in an inviting low curling cross to an unmarked Walker at the far post and he seemed set to score only to sidefoot his six-yard effort against the woodwork.
The miss proved crucial as, almost immediately, Doncaster went up the other end and won a penalty for Peter Clarke holding Jason Price.
Stock stepped up to take the penalty and was the epitome of coolness as he confidently rolled it home as keeper Darryl Flahavan dived to his right.
606: DEBATE
It soon got worse for Southend with Doncaster extending their lead through Barrett's own goal.
In truth, the Southend skipper could do little else but deflect the ball in under pressure from Price after Paul Green nodded a deep cross just under the crossbar.
Doncaster's passing football was proving too much for the Shrimpers and Coppinger slalomed through the visitors' defence and clinically finished to compound the visitors' misery.
Coppinger's ability to run with the ball and glide past defenders was a fantastic weapon in Doncaster's armoury and he used to it to great effect to add a fourth.
He picked up the ball midway in the Southend half on the right of midfield and angled a run into the area before driving in a superb left foot shot.
Doncaster boss Sean O'Driscoll had the luxury of taking off key players ahead of the final but he left Coppinger, who will have given watching Leeds manager Gary McAllister plenty to think about.
Coppinger completed his hat-trick by angling in a free-kick before Bailey grabbed a late goal for a Southend side overwhelmed by their rivals.
Doncaster boss Sean O'Driscoll:
"The job is half done and we want to finish it against a very good Leeds team.
"We've performed like that for most of the season and sometimes you don't get your just rewards.
"It's probably fitting in an important game like this we have finished some of the moves we have done all season."
Southend boss Steve Tilson:
"If James Walker had taken the chance early on instead of hitting the crossbar it may have been a different game.
"But credit to Doncaster. They played very well.
"They showed why I think they are the best footballing side in this division. I would love to see them now go on and get into the Championship."
Doncaster: Sullivan, O'Connor, Mills, Hird, Gareth Roberts (Guy 68), Green, Stock, Wellens (McCammon 73), Coppinger, Price (Taylor 76), Hayter.
Subs Not Used: Smith, Lee.
Goals: Stock 11 pen, Barrett 21 og, Coppinger 39, 52, 80.
Southend: Flahavan, Francis, Clarke, Barrett, Mulgrew, Moussa, Bailey, McCormack, Gower, Barnard (Revell 62), Walker (MacDonald 62).
Subs Not Used: Collis, Liptak, Black.
Booked: Barnard, Bailey, Mulgrew.
Goals: Bailey 88.
Att: 13,081
Ref: Mark Halsey (Lancashire).
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