Rosalie is nice but I love Ailsa and Ophelia. Also think Arriety is gorgeous but it's so obviously Borrower, I'm not sure I've ever heard it used anywhere else. You couldn't have Ailsa Elsa though, and Ophelia Elsa doesn't sound great either.
For boys I love Ellis and quite like Edison and Morris. It's a shame Harris is out, that would have been my favourite too.
From your suggestions how about:
Ailsa Rosalie May
Rosalie Ailsa May
Ophelia May
Ailsa Meredith
Rosalie Arietty May
Athena Rosalie May
Edison Morris
Morris Albin
Ellis Theoden
Reggie Theoden
Edison Otis
Ellis Murphy
Other suggestions on a similar theme.
Girls:
Ariadne, Anya, Aria, Aliya, Ariana, Alyssa, Alicia, Arabella, Athene, Mallory, Melody, Morven, Mirren, Morag, Madeleine, Mirabelle, Melisande, Millicent, Octavia, Olivia, Rosemary, Rosalind, Rosanna, Roxanne, Robina, Rowena, Romily, Rowan
Boys:
Austin, Aaron, Aiden, Elliot, Emerson, Ethan, Maddox, Mason, Morgan, Orson, Oakley, Owen, Reuebn, Riley, Ryan, Rhys, Ronald, Teo, Theo, Theodore, Thor, Torin, Tian.