Rossair was a flying school, aircraft maintenence operation and Cessna dealer for years. Did all my flying with them and they were great because when you needed to fill the gap between PPL and CPL you delivered aircraft, for free - excellent.
I know Frank Calder who was one of the directors company passed away and then after that I think the maintenance operation got sold off and the dealership for cessnas eventually stopped or went interstate (unsure here) then all that was left was the flying school which persisted along for a few years (and was I think owned by a former staff member from the old flying school at Parafleld) then closed.
I am unsure of the current Rossair charter operation ownership but I believe a few of the guys who trained me yonks ago are still flying there.
Hope this helps