The Master Surname Index (not online) (mostly burials in Alberta cemeteries) of the Alberta Genealogical Society lists 16 ROSSMAN names, 14 of these are in the Barrhead area, but no Leona or Robert.
Robert BOSSMAN is mentioned on page 112 of the Book 'Trails Northwest, Barrhead' published in 1967.
There are 7 ROSSMAN phone listings, give them a call, they must know something. http://www.canada411.ca/
For further research please contact the AGS Research Services Committee of the Edmonton Branch, http://abgensoc.ca/