Talofa Chris and thank you very much for this information.
I already had baptizimal records for Luisa and her siblings but the dob variation for Silveria is new to me. It may be the answer to a question I've had for a long time which is, why is there a 5 year gap between the two middle children? My father always believed that his Aunty Silveria was older than his Uncle John and this may well confirm his belief and answer my question.
Your information on Luisa's parents is the most solid I've had to go on so far and in sharing it with my father, he is now recalling memories from his childhood long forgotten.
I was aware of the difference in the spelling of our surname also. Its yet another question I hope to find answers to. All the decendants of the four siblings (now five generations worth) use the spelling ROACHE so it leads me to believe that either the records are incorrect or our great-great-grandfather Frank himself altered the spelling for some reason.
I know that there are some original records of British subjects in Samoa during the late 1800 period held here in the NZ Archives. That'll be my next stop.
Thanks again for your help. Its invaluable.