Crusaders (12) 30
Tries: Martin, O'Hara, Hanbury, Sammut, Dyer Goals: Schifcofske 5
Hull KR (6) 24
Tries: Fox, Briscoe, Welham, Galea Goals: Dobson 4
Brian Noble, sacked by Wigan a year ago, has worked miracles in Wrexham
Brian Noble's Crusaders completed one of rugby league's great feats as they qualified for the Super League play-offs in his first season in charge.
Crusaders, 12-6 up at the break, were stunned by two tries in four minutes from Shaun Briscoe and Kris Welham.
Rhys Hanbury and Jarrod Summut replied with a two-try burst of their own.
But, despite Ben Galea pulling Hull KR level again, Clinton Schifcofske's sixth goal gave breathing space before Luke Dyer's late, clinching try.
Crusaders ' victory put them back into eighth spot as Castleford, who had started the day there, went down 40-30 in another nailbiter against St Helens at Knowsley Road.
And that completed a remarkable transformation for a team which finished bottom of Super League 12 months ago with only three wins to their name, nearly went out of business and were still being hastily reassembled by Noble when the Super League season kicked off at the Racecourse back on 29 January.
It was a night of high drama on and off the pitch at the Racecourse Ground.
Visitors Hull KR received a boost before kick-off, both with the signing of Australian international Willie Mason and the news that rivals Hull FC had gone down to defeat earlier in the day to set up a mouth-watering Humberside derby play-off clash next weekend.
Crusaders made one change from the side who found St Helens too powerful at Wrexham a fortnight ago, the inspirational Jarrod Sammut returning at half-back, with Peter Lupton moving to loose forward and Frank Winterstein dropping to the bench.
Rovers brought in centre Kris Welham, who has been out of action for two months with a shoulder injury, while forward Ben Galea was back after an eye problem.
The Welshmen were ahead inside five minutes when front rower Ryan O'Hara capitalised on pressure in the visiting 25 to go through a half-gap in the Rovers defence, full-back Schifcofske converting.
But, when Schifcofske missed a high up-and-under on the sixth tackle, Rovers winger Peter Fox was in at the corner, Michael Dobson levelling with a touchline conversion.
Welsh pressure told when a cross-field kick on the sixth tackle by lively scrum-half Sammut saw Dyer climb high and throw a speculative pass to the right wing, where centre Tony Martin cashed in.
The half was marred by a big fight involving both sets of players after an off-the-ball incident which saw Lupton and Rovers' Ben Cockayne warned by referee Robert Hicks.
The second-half was just as intense, exploding into life when full-back Briscoe and centre Welham put Rovers into an 18-12 lead.
But, by 53 minutes, the Crusaders had restored their six-point lead, Hanbury going over on the left before an astonishing sprint by Sammut, who intercepted an attack on his own line and run 100 yards for the try.
Schifcofske each time kept up his record with the boot but Rovers hit back again when Galea drove over from a couple of yards and Dobson's fourth conversion levelled the match.
With eight minutes left, Schifcofske booted a 25-yard penalty to give Crusaders a 26-24 lead.
And that set the scene for Dyer's last-ditch try to secure their historic play-off place - and a trip to Huddersfield next Saturday (1545 BST).
Crusaders coach Brian Noble:
"Over the last 10 or 11 years, if you play well on the day, you win. It is cup football from now on. In essence, we had our first warm-up game because it was trapdoor football for us. If we didn't win, we were out.
"We set ourselves a goal and I thought we did it the hard way at times tonight. It was probably fabulous to watch but not fabulous on the ticker.
"But I recognise absolutely how good Huddersfield are so we will have to be good to get them.
"You have to dream big. Life, in general, you have to have a vision and say 'I can take these blokes anywhere'. I still think I can and I have not lost faith in any of them."
Hull KR coach Justin Morgan:
"We are delighted with Willie's signature. He is a high-profile player and he will add plenty to this team.
"But we have got to get 2010 out of the way first and now, effectively, our season starts all over again."
Crusaders: Schifcofske, Dyer, Martin, Mellars, Youngquest, Sammut, Hanbury, O'Hara, Withers, Bryant, Hauraki, Chan, Lupton.
Replacements: Lee, James, Peek, Winternstein.
Hull KR: Briscoe, Fox, Welham, Cockayne, Colbon, Murrell, Dobson, Vella, Fisher, Clinton, Newton, Galea, Lovegrove.
Replacements: Wheeldon, Watts, Hodgson, Netherton.
Referee: Robert Hicks (Oldham).