Rockwell enjoyed the better of the exchanges in the opening half and Bill Johnston put them ahead with a penalty after seventeen minutes. Mikey Wilson increased the lead with a try five minutes later to lead 8-0 at half time.
Full back Stephen Quirke extended Rockwell's advantage with a try after forty five minutes.
Munchin's rallied in the closing stages, a try by skipper Adam Moloney brought Munchin's back into contention and Jason Kiely converted.
In an exciting finish Kiely closed the gap with a penalty, but a determined Rockwell side held on for victory.
Rockwell: Stephen Quirke; Charlie Manton, Lee Molloy, Blake Ryder, Tim Brennan; Bill Johnston, Daryl Egan; Niall Campion, Ben Murray, John Tierney; Jack Binchy, Conor Cashman; Jack Kennedy, Darren Fehilly, Mikey Wilson. Replacements: Sean O'Brien, James Kendrick, Conor Beary, Morgan Irwin, Leigh Devereaux, Keelan Looby, Kieran Moynihan, Jamie Stone St. Munchin's: Jonathan O'Hanlon; Cameron Stephenson, Matthew Lyons, Sean Kelly, Marcus Browne; Jason Kiely, Brian Bennett; Emmett O'Callaghan, James Burke, Ronan Kirwin; Sean Hayes, Conor Radcliffe; Adam Moloney (capt), Aaron McNamara, John Foley. Replacements: Evan Quinlivan, Colin Kelly, Kieran McGuirk, Hugo McDonald, Shane Corbett, Kieran Galvin, Adam Guerin, Evan O'Connor