They now meet CBC in the semi-final, encouraged by an impressiveperformance, especially in the first half after which they led 12-3 in spite of playing against the strong wind.
Castletroy, well led by captain Conor Bonfil and with half-backs Jonathan McDonnell and Luke Clohessy also doing well at half-back, proved gritty opposition but lacked the physical strength to cope with the powerful Rockwell forward pack.
The champions are well led by second-row Sean McCarthy who was outstanding throughout while the front row of Jack McCormack, Darragh Mulcahy and James Maxwell proved a powerful unit and will not be easily contained in the games to come.
Out-half Aidan Moynihan also made a telling impact and opened the scoring in the 12th minute scoring at the posts for a try that he converted himself.
Rockwell coped admirably with playing into the elements, keeping the ball tight for the most part but also willing to move it wide on occasions.
It was a strategy that paid a further rich dividend on 20 minutes when the issue was more or less sealed as winger Alex Lynch finished off a fine attack in the right corner to move his side 12-0 ahead.
McDonnell knocked over a Castletroy penalty before the interval and on the turnover did well to restrict Rockwell to a try by centre Killian Kiely and a penalty by Moynihan.
ROCKWELL: D Johnston; A Lynch, R Jermyn, C Kiely, S McMahon; A Moynihan, D McGagh; J McCormack, D Mulcahy, J Maxwell, S McCarthy (capt), D Foley, A Sweeney, S O’Dwyer, A Butler.
Replacements: A Barron for McGagh; C Ryan for Mulcahy; R Lyons for McCormack; W O’Dwyer for Maxwell; J Feehan for Sweeney; R Maher for Lynch; S O’Donoghue for Jermyn.
CASTLETROY: S Moran; D Grant, E Clancy, W Shanahan, K Enright; J J McDonnell, L Clohessy; J Tiernan, L Cronin, S Shinners, P Butler, P Bermingham, J O’Neill, B Burns, C Bonfil (capt).
Replacements: T Kelly for Tiernan; R Sweeney for Cronin; D Kennedy for O’Neill; J Murphy for Carroll; P Butler for Grant.
Referee: K Imbush (IRFU).