Dear Eileen There are about 29 listings inthe Argentina Telephone directory for the fmaily name DE ROSAS and none of them are RICARDO as a first name (first names run in families usually but here none are listed as Ricardo.) I checked the ellisisland.org website and I found one 13 De Rosas entering the USA as an immigrant and none are listed as Ricardo De Rosas but I did come across a Pasquale De Rosas who was a radio operator on a ship (was this his job on the ship as a crewman???).
If you go to www.telezplorer.com.ar and where it says "apellido" just type in De Rosas and all 29 listings will come up by fullname and addresses. perhaps you might know the name of his brothers and they might be listed.
Were his parents Italian or just Argentinian?
Do you know where they lived in Argentina..Any information might seem trivial to you may be very important for us to locate his family..like where did tjhe family live in Argentina???? Petertimber