Beaten by Rovers� neighbours Hull FC at the same stage and on the same Huddersfield venue 12 months earlier, Saints ensured there would be no hint of a repeat as they turned on the style with a nine-try feast.
Australian centre Jamie Lyon grabbed 18 of his side�s points with a try and seven goals while Great Britain full-back Paul Wellens cashed in on the spree to score his 100th try for the club as Saints booked their trip to Twickenham, scene of their 2001 triumph over Bradford Bulls.
Former Hull KR second rower Jon Wilkin helped lay the platform for the rout with two first-half tries but the 2004 winners were hugely indebted to the playmaking brilliance of Great Britain duo Sean Long and Keiron Cunningham.
The occasion was something of an anti-climax for the 5,000 Hull KR fans among the 12,868 crowd at the Galpharm Stadium.
Rovers, surprise quarter-final winners over Warrington Wolves, never looked capable of overturning the odds, although they did not have the best of luck.
Second rower Jason Netherton went off a minute into the match after a clash of heads with team-mate Byron Ford and returned half-an-hour later to find his team 24-0 down and out of the game.
Stand-off Gareth Morton, a replacement for the injured Scott Murrell, himself limped off before half-time and skipper James Webster went off with a cut face early in the second half.
A full-strength Robins would most probably made little difference since most engage Super League teams would have struggled to contain Saints on this form.
The defeat might have been even worse had Rovers prop Makali Aizue been sent off instead of being put on report for a high tackle on Long in the 27th minute.
Rovers had no answer to the darting runs from dummy half by Cunningham or the offloading from the tackle by front rowers Paul Anderson and Jason Cayless which set up early tries for Long and Wilkin.
Monstered up front, the National League team were also out-muscled by the Saints backs, with stand-off Leon Pryce and centre Willie Talau demonstrating awesome strength to break the first tackle.
The contest might have been closer had video referee Ian Ollerton given them the benefit of the doubt when Webster�s kick bobbled and ricocheted in the Saints in-goal area and Tommy Gallagher got the final touch.
Gallagher, a loser with Toulouse in last year�s semi-finals, could have had a hat-trick of tries had his side been able to match the clinical finishing of the engage Super League leaders, for he twice went within inches of touching down in the second half.
Saints, on the other hand, finished just about every tryscoring opportunity they created and also had a try by Paul Anderson disallowed by the video referee.
The ball bounced kindly for Wilkin to claim his second try and, when second rower Vinnie Anderson twisted and turned out of a series of tackles to score his side�s fourth try 10 minutes before half-time, that was the signal for Saints coach Daniel Anderson to rest the influential Cunningham.
As hard as he tried, James Roby was no substitute for the Great Britain hooker, whose temporary absence enabled Rovers to stem the tide, largely through the efforts of the untiring Gallagher.
It was a brief respite, however, with Cunningham returning in time to watch Long send Lyon over for the first try of the second half.
As Saints maintained their stranglehold, man of the match Talau went over for two tries in 10 minutes and winger Ade Gardner and Wellens also got in on the act as the engage Super League side reached the half-century mark.
Rovers still have their main ambition of promotion to engage Super League intact but the size of the defeat will be a sobering experience.
Hull KR: 0
St Helens: (24) 50 Tries: Long, Wilkin (2), Anderson, Lyon, Talau (2), Gardner, Wellens Goals: Lyon (7)
Hull KR: Cockayne, Steel, Couturier, J. Goddard, Ford, Morton, Webster, Aizue, Fisher, Tangata-Toa, Morrison, Netherton, Gallacher. Replacements: Joseph, Rivett, Garmston, Barker.
St Helens: Wellens, Gardner, Lyon, Talau, Meli, Pryce, Long, P. Anderson, Cunningham, Cayless, Wilkin, V. Anderson, Graham. Replacements: Roby, Fozzard, Gilmour, Fa'asavalu.
Referee: K Kirkpatrick (Warrington)