A professional second-half performance and a stunning Steve McMahon try gave Rockwell a winning start to the defence of their senior crown at Clanwilliam.
The champions came from behind to record an impressive win, aided by a powerful performance from flanker Tommy Anglim.
Crescent deservedly took the lead when full-back James Frawley completed a fine move to touch down.
Rockwell hit back within three minutes with a Rory Parata penalty and went in front on the stroke of half-time when Aidan Moynihan found a gap in the defence to score under the posts. Parata added the extras, making it 10-5 at the break.
After repelling the Crescent attack, Rockwell sealed victory with a sublime try as full-back McMahon broke down the blind side, beating several tackles before crossing.
Rockwell College – S McMahon; D O'Mahoney, S O'Donoghue, R Parata, W Coffey; A Moynihan (R Horgan 65), B Riley; D O'Connell, S McNulty, J Maxwell; N Flynn, A Horgan (J Feehan 51); S O'Connor, T Anglim, S Dwyer.
Crescent Comprehensive – J Frawley; J O'Sullivan, JJ O'Neill, J Purcell, J Hogan; G Lyons, G Fitzgerald; M O'Donnell (G Mullins 48), J Green, L McMahon; J Keane, E Casserly; C Blake, J Kavanagh, J Dineen (D Dee 55).