Second five Richie Levita added the extras which gave WBHS the early ascendancy.
Rosmini were 2016 and 2017 champions for a reason and soon switched the momentum with excellent tactical kicking. A grubber led to their opening try to square the ledger.
WBHS worked their way back into Rosmini territory and crossed for their second try of the afternoon through prop Ethan Wikaira. However, a late penalty brought Rosmini back within two points at the halftime break.
Lock Allan Craig and blindside flanker Brody Cameron were standouts in the pack throughout the match while Levita, first five Max Brunker and fullback Rocky Olsen controlled the game well in the backline.
The rain really set in during the second stanza, resulting in close-to-the-chest rugby from both sides as neither risked sending the ball wide.
Rosmini slowly worked their way deep into WBHS territory and were rewarded for their patience with an unconverted try with five minutes left.
However, an indiscretion 40m out from their line threatened Rosmini's chance at victory.
Levita stepped up and slotted the penalty goal with two minutes left on the clock to tie things up.
The scores remained level at the fulltime whistle, both sides leaving with deserved points.
WBHS are back on the road next week when they take on Takapuna.