Daisy can use a landing mixup with her float. She has a fairly good disadvantage against roy and many sword characters. Try to float above and bait out a move, then drift away and land. You can airdodge down if you have to, but try to save it so you can waveland into a more strategic position. Roy doesn't have any juggling moves that stay out for a long time, so you shouldn't have too much trouble.
Daisy