Rose is a beautiful name, whether on it's own or as a nn for a longer
Rose name. I don't think it would be an issue having
Rose as a full name. I like the sound of
Rose with
Tobias and
Sebastian too.
By the way, I adore your name! Millie/Milly has been a fave of mine for years and a name I would seriously consider using in the future for a DD of my own. It's a gorgeous name.