Michael Dobson landed a dramatic 75th-minute penalty to hand Hull KR a famous victory and wreck St Helens' hopes of drawing level on points with leaders Leeds.

Sean Long's 70th-minute drop-goal handed Saints a 19-18 advantage but they were punished five minutes later when Dobson slotted a routine penalty to give Rovers victory.

Three times Saints led through converted tries from Tony Puletua, Gary Wheeler and Paul Wellens but three times Rovers hit back with scores from Ben Galea, Peter Fox and Jake Webster.

Talismanic scrum-half Dobson added the extras to each try to tie the scores at at 18-18 before Long found the space from 25 metres to engineer a one-pointer to put St Helens on course for victory.

Yet Justin Morgan's spirited men hit back through Dobson's penalty and at the final whistle their supporters celebrated as if their team had reached the Grand Final at Old Trafford.

That nine of Saints' 17 players on duty progressed through the academy ranks at Knowsley Road served only as consolation for Saints.

They needed to win by 16 points or more to replace fierce rivals Leeds at the summit of the engage Super League and they could not do it as Rovers claimed a momentous success.

The visitors were vibrant throughout and only some desperate last-ditch defending from St Helens kept them at bay in the opening exchanges.

Rovers - commanding respect after two years in Super League - continued to probe with Dobson at the heart of all their promising moves.

However, the hosts enjoyed a purple patch which reaped rich rewards in the 15th minute when Puletua - Saints' only close-season signing - showed formidable strength to burrow over from close range.

Long kicked successfully to put Saints 6-0 ahead but Rovers responded in style and came up with a try in the 22nd minute that typified their bold approach.

Dobson was the architect, finding Galea charging forward at pace 12 yards out to crash under the posts and sent the large contingent of travelling fans into rapture.

Dobson added the routine conversion to the scores at 6-6, yet the momentum quickly returned to St Helens and Matt Gidley's forward pass to Wellens spoiled what should have been a fine try down the right flank.

Puletua, at 17 stone a formidable presence, continued punching holes up front and he was in the thick of a bewildering move in the 32nd minute which culminated in Andrew Dixon ushering fellow replacement Wheeler over in the left corner.

Long converted from a difficult angle to put Saints 12-6 ahead at the break but Rovers again found a response after a vibrant start to the second half.

An equalising score arrived in the 44th minute when Dobson's kick down the left flank was not dealt with by Gardner, allowing Chev Walker to collect the loose ball and produce a neat short offload which sent Fox scampering over in the left corner.

Dobson's superb conversion levelled matters at 12-12 but parity only lasted for three minutes as Long sent Paul Wellens over the whitewash and then added the conversion.

That put Saints 18-12 but Webster touched down after a kick from Dobson, who converted for 18-18 before Long's drop-goal edged Saints back in front.

Rovers were not to be denied, however, and victory was theirs in the 75th minute when St Helens were not square at the play-the-ball and the resultant penalty from Dobson decided matters.