Hi Jo - you know, you could probably buy a phone card which would give you a cheap phone call to Oz.
If you look in the white pages (phone listings) there are some current ROSER entries listed living in Carrington which is a suburb of Newcastle also. Sometimes writing is best though as it gives the recipient time to 'digest' the information.
http://www.whitepages.com.au/ put in the surname and Newcastle as the place, in the residential section.
Ivan died in 1971
NSW, registered Newcastle #81856
1971
Ivan William ROSER, parents James William, Hilda Emma.
Electoral rolls:
1949
Ivan William ROSER, constable and
Alice Catherine ROSER at 18 Denison St, Mayfield.
His parents are just along the street at 25 Denison St.
Odd - can't see him after that, although 1954-1963 Alice Catherine was with her parents at 23 Milson St Charlestown. Perhaps they separated/divorced. (Unfortunately NSW BMD indexes do not show marriages later than 1962, nor births after 1912).
However there are ROSERs in Carrington in 1930. L
Looking on TROVE there are many entries for ROSER, some quite early - 1857.
http://trove.nla.gov.au/newspaperJudith