The Master Surname Database (not online) (mostly burials in Alberta cemeteries) of the Alberta Genealogical Society does not list the ROSEBROOK name and no Mary Blanch WEBBER and no John Frederick WEBBER that fits your query.
Your ROSEBROOK is in the AGS Homestead Index.
For further research please contact the Research Committee of the Edmonton Branch. You may want to check with the AGS Lethbridge Branch.
http://abgensoc.ca/Peter