Thanks for the information, if it aids identification I can tell you that it was roughly the same size as a mallard. How rare are ross's geese if they are rare at all?
This link points out that a rosss's goose has a rounder head than a snow goose which certainly does concur with the pictures. The size of the bird was the one thing that bothered me but having looked it up on the web it has a very rounded head which again fits the bird.
Snow Geese (near the bottom)