It was the 84th minute of a remarkable match with many mistakes but endlessly enterprising attacking play when Roper took a pass from Lee Briers to force his way over. It was a tribute to Warrington's resilience, but a heartbreaker for Hull, who had looked the more likely winners throughout.
Hull took the lead three times in the first half, initially when Logan Campbell, who was only playing stand-off because of Hull's shortage of half-backs, showed the classical skills of the position by weaving through for a try.
Warrington's first equaliser came when Brendon Tuuta's pass was picked up by Chris Rudd, who got the ball out of Steve Prescott's tackle for Lee Penny to touch down.
If Prescott was at fault there, he made up for it with the 40-yard kick- and-chase that kept him just in front of Briers to put Hull back in front.
Back came Warrington as a game of tremendous ebb and flow continued, Steve McCurrie getting out a miraculous pass as he went to ground for Danny Farrar to score. When Hull hit the front again, Fili Seru's strength allowing him to plunge over in the corner, they at least stayed there till the break.
Better still, Hull extended that lead early in the second half, Gary Lester wriggling his way through a series of tackles and Graeme Hallas' third goal giving them a 10-point margin.
But just when Hull should have been consolidating their advantage, they allowed Penny to run through unmolested for his second try.
Almost midway through the second half, the determined visitors drew level, Rudd coming from just onside to take Briers' cleverly flighted kick.
A marvellous second try from Seru, their Fijian winger, put Hull back in the lead, if not in control. Briers and Mike Eagar fashioned yet another equaliser for Warrington and both Roper and Briers failed with drop goal attempts before Roper decided it.
Hull: Prescott; Seru, Hunte, Hallas, Baildon; Campbell, Lester; Craven, Hepi, Okesene, Booth, Schultz, Busby. Substitutes used: Stephenson, Leatham, Nolan.
Warrrington: Penny; Rudd, Eagar, Kohe-Love, Forster; Roper, Briers; Chambers, Farrar, Nutley, McCurrie, Tuuta, Wainwright. Substitutes used: Morley, Hilton.
Referee: S Presley (Castleford).
l Wendell Sailor, the Australian Test winger who was due to join Wigan next season on two-year contract worth pounds 500,000, has has opted instead to stay with Brisbane Broncos.Reuse content