Questions – The Roll - Automatically organize and find the best photos in your camera roll Review

My whole photo library is in iCloud Photo Library. Does this app copy images to my device to analyze and rate them? Or does it leave them in the cloud so I can continue to save disk space on my phone? Is there a way to mark false duplicates and separate them out?
Review by scottyp08 on The Roll - Automatically organize and find the best photos in your camera roll.