Roy came into use in the late 19th century, probably influenced by the main character of Sir Walter Scott's novel Rob Roy, in which the historical character Robert M'Gregor is nicknamed Roy for his red hair.
There have been lots of notable non-country namesakes, including baseball's Roy Campanella, humorist Roy Blunt, Jr., Walt's brother and partner Roy Disney, singer Roy Orbison and pop artist Roy Lichtenstein. Roy Hobbs was the protagonist of the Malamud novel The Natural, played in the film by Robert Redford.
Roy was also the first name of clothing designer Halston.
If girls have adopted Ray, why not Roy.