Despite dominating possession for long periods Christians were unable to convert their chances into scores and this proved their undoing as Rockwell's only attack in the opening half produced a try on the stroke of half time.
Christians started the hungrier side and had Rockwell on the back foot from the kick off but for all their efforts a Dave O'Riordan drop goal and two penalty attempts at goal which all fell short of the target was all they had to show.
Just on the stroke of half time Rockwell brought play into the Christians Twenty Two and won a scrum against the head and the ball was spread out to winger Steve McMahon who scored in the corner for a 5-0 interval lead for the Tipperary side.
Christians began the second half on the attack with John McCarthy, Charlie O'Regan, Tadgh Arrigan and Darragh Moloney looking to punch holes in the Rockwell defence, but superb defensive work kept the Sydney Hill School at bay.
Rockwell when in attacking positions put points on the board with Aidan Moynihan kicking two penalties on 51 and 59 minutes.
Christians did rally in the final few minutes but just were unable to pierce a solid Cashel defence where David Johnston and Rob Jermyn were outstanding.
Scorers Rockwell College: Steve McMahon try, Aidan Moynihan 2 pens.
C.B.C.: Thomas Quinlan, Chris McAuliffe, Tom Morehead, John McCarthy, Gerry Ryan; Dave O'Riordan, Charlie O'Regan; Charlie Slowey, Rory Daly, Rory Burke; Tadgh Arrigan, Darragh Moloney; Andrew Mintern, Michael Ryan, Dylan Stokes.
Replacements: Michael Lordan, Devin Fitzgerald, Shane Galvin, Rob O'Dowling, Adam McCarthy, Ryan Foley, Cillian Monohan, Joe Dowling.
Rockwell: David Johnston; Alex Lynch, Rob Jermyn, Cillian Kiely, Steve McMahon; Aidan Moynihan, Dylan McGagh; Jack McCormack, Darragh Mulcahy, James Maxwell; Sean McCarthy, Darragh Foley; Aaron Sweeney, Sonny O'Dwyer, Aidan Butler.
Replacements: Sean McNulty, Robbie Lyons, William O'Dwyer, Neville Flynn, James Feehan, Aidan Barron, Sean O'Donoghue, Ronan Maher.
Referee: Eddie Hogan O'Connell (M.A.R.).