Are you talking about a heraldic device or emblem? There are organizations which will mail you the supposed heraldic emblem for your last name, but unless you actually happen to be a member of the Peerage, these heraldic emblems don't really apply to your family, even if your particular family does happen to share the same last name with someone who is descended from royalty.
But I'm really not sure what you're talking about here, regarding a "symbol" for Ross. Can you be more specific?
-- Nanaea