A tremendous second half performance with 10 men, full of all the qualities that have depicted this side this season, saw the Millers pull off a superb win to lift them into third place.
They deserved every clap of the rousing ovation for the way they played in a thrilling second half although the downside was that midfielder Richie Smallwood will miss the first leg of the Play-off semi-final after being sent off right on half-time.
Despite that blow, manager Steve Evans still went for the win and rarely, if ever, can a side with 10 men have gambled like this and played a 3-3-3 formation.
“It’s essential to try and win every game and even a man down we were going to have a go,” said the Millers boss.
“We got desire, commitment and passion in that second half and you saw how the fans responded to what they’d seen.”
He said they would look at the Smallwood incident again - “I think we were all stunned by the red card,” said Evans - but if it was high then there would be no appeal.”
His absence will make it more important that Lee Frecklington is available and it will have pleased Millers fans that he was joining in the pre-match workout and may well figure next Saturday.
The decisive goal, for which they had worked so hard, came from that man Kieran Agard with 11 minutes left and was his 25th of the season.
Joe Skarz broke forward, James Tavernier challenged for the cross and it broke for Agard to finish off with a low right footer typical of so many of his goals this season.
With Alex Revell rested, Rotherham had look to take a different attacking route than usual with Haris Vuckic dropping off behind recalled Wes Thomas.
In fact it might have paid off early on had Nicky Adams, receiving from Vuckic, not blazed over from 18 yards.
After their bright start, Rotherham had Adam Collin to thank for not being behind, diverting away a Chris Birchall volley from 12 yards.
Thomas, wanting to make an impression, was twice denied inside 60 seconds, Sam Johnson tipping his shot over and, from Ben Pringle’s corner, his header was brilliantly turned over by the keeper. .
Johnson then diverted a Tavernier shot behind with his leg after Ben Pringle had picked out the right back’s run.
Then the game turned for Smallwood. Firstly a goalbound shot struck Thomas and he looked sure to net the the rebound but Duffy diverted the shot behind with his head.
Then came Smallwood’s red card with referee David Coote feeling he was reckless when catching Billy Knott with his studs as he challenged for a ball he had lost control of.
The dismissal prompted a double substitution at half-time with Milsom and Agard replacing Adams and Vuckic - and within 25 seconds Agard glanced a header narrowly wide.
The big gamble came when Revell replaced Michael O’Connor Tavernier moved into midfield to make it 3-3-3.
Revell’s introduction had an almost instant pay-off, his header being superbly saved by Johnson.
It had developed in a tremendous battle settled by Agard’s goal instinct and Rotherham deserved their stoppage time break when Carl Dickinson’s header from a corner deflected off a post.
It was a win that ended a run of six straight defeats against Vale.
ROTHERHAM UNITED: Collin 8; Tavernier 8, Morgan 8, Arnason 8, Skarz 8; Adams 6 (Agard ht, 7), O’Connor 7 (Revell 70, 6,), Smallwood 6, Pringle 8; Vuckic 6 (Milsom ht, 8); Thomas 7. Unused: Shearer, Davis, Addison, Hitchcock.
PORT VALE: Johnson 8; Yates 6, Robertson 7, Duffy 6 (Williamson 50), Dickinson 7; Dodds 7, Birchall 6 (Myrie-Williams 70), Knott 6 (Shuker 70), Lloyd 6; Hugill 6, Tomlin 6. Unused: Griffith, Smith.
Goal: Agard (79).
Referee: David Coote (Notts).