The underdogs made an inspired start and registered their first score after 12 minutes when out-half Bill Duggan knocked over a penalty having missed one previous.
The tide quickly turned in Terenure’s favour when lock Aiden McGrath was penalised for not rolling away from a ruck and full-back Ryan Roopnarinsingh kicked a simple penalty.
Terenure had a chance to move ahead when Roopnarinsingh went close from a penalty on the right but missed the opportunity in a frantic opening half.
Out of nothing Roscrea scored their first try when full-back Philip O’Dwyer’s moved out of the defence, he slipped to Shayne Layden whose kick ahead was somehow controlled by replacement Maurice Fitzgerald short of the line for a try to make it 8-3 right on half-time.
Roscrea stormed forward on the restart back and incredibly, decided to turn down a kickable penalty in favour of a lineout and maul that came to nothing.
The Dublin school reacted by introducing four replacements simultaneously but the move yielded little reward when Roscrea hooker Denis O’Dwyer crashed over for his side’s second try after being fed by Mathew Mellott, who intercepted a pass as the other end.
Duggan added the extras for a 15-3 lead in the 48th minute.
Terenure responded with a try of their own by winger Philip Smith, who just got outside full-back O’Dwyer to cut the gap to seven. It was shortened to four by fly-half Danny McCormack’s penalty in the 66th minute ahead of a pulsating finish.
Scorers for Cistercian Roscrea: M Fitzgerald, D O’Dwyer try each; B Duggan pen, con.
Scorers for Terenure College: P Smith try; R Roopnarinsingh, D McCormack pen each.
P O’Dwyer; C Brennan, S Layden, C Finn, M Mellotte; B Duggan, G Gallagher; G Fallon, D O’Dwyer, C Farrell, A McGrath, R Maloney, A Henderson, E Quirke, C Maloney.
Replacements: M Fitzgerald for Brennan 34 mins; O Heffernan for Farrell, J O’Driscoll for O’Dwyer both 62 mins; R Mooney for Henderson 69 mins.
R Roopnarinesingh; S O’Loughlin, C Quigley, D Olin, P Smith; D McCormack, R Barry; P O’Reilly, J Carroll, S Borza; R Malone, R Somerville; B Twomey, N Lalor, G Furlong.
Replacements: C Owens for O’Reilly, E Kelly for Malone, C Simpson for Twomey, C Jones for Olin all 44 mins; J Kirwan for Somerville, D Hynes for Carroll both 62 mins.
J Montayne, Leinster Branch.