For keyword searching in Voyager and OneSearch, try Pitcairn Islands history, Pitcairn Islands ethnology or Pitcairn Islands genealogy. When searching in the Hawaii-Pacific Journal Index, your best bet is to use only the word Pitcairn as a keyword anywhere search.
You can find information on certain Rotuman gods that are related to creation stories in the Dictionary of Polynesian Mythology (see page 331 for a list of creation deities from throughout Polynesia, then look up the Rotuman gods by their names in the front of the dictionary). When searching in Voyager or OneSearch, try keywords like Rotuman legends, Rotuman myths or Rotuman folklore.