I have looked into rooves and yes it is more common in Ireland.
David Crystal's books about the origins and development of the English language are very informative. When I have time I'll post a link here. Basically there are more non native English speakers and people with English as a second language than there are native hence many existing varieties exist already none of which could be said to be grammatically correct or not which poses a few issues for English language teaching.

There is also a large Northern Irish influence on NZ and American English which might explain the use of rooves in NZ where many of my distant relatives have ended up! It certainly explains why the English eat spring onions and the Irish and Americans eat scallions!