Seems pretty daft to me. I've never seen it used IRL, in fact I've only ever seen
Princess and
Queen used as given names. A family member, who was a lecturer, had a class once that contained a
Queen Elizabeth Lastname.
If people want a longer form of
Roy, so that
Roy could be a nn, I suppose
Royal would do. But I don't see the point. My BIL (Scottish mother) is
Roy, and appropriately has red hair. Probably because of him, I like
Roy very much.