I take it they were displaced persons (DPs) from Lithuania who emigrated to Australia after being in Germany or Austria.
To get information about them, contact the International Tracing Service (ITS) in Bad Arolsen, Germany. You can submit an on-line research request at:http://www.its-arolsen.org/en/homepage/index.html
I did research there for a week in May 2008 looking for documents regarding my father's time as a DP in Germany before he emigrated to the U.S.
There was a priest named Sadauskas who was a pastor of the Catholic church in Virbalis, Lithuania. I was told he was originally from Rumsiskes and he is buried next to the church in Virbalis.
I too am researching the Sadauskas surname and would be interested in what you find out.