Even shoes which just have a small amount of material covering the ankles, is a lot better than having no ankle support.
If you tighten your shoes properly then you can feel the difference, it makes it a LOT harder to roll over onto your ankle, so I would defo have ankle support now, as it does make you feel more comfortable on the bike, and when you jump back and your ankle goes to roll, your foot kind of stops and springs back.
Trials shoes = well worth it, whether it be ribo, koxx, yik or monty, they are worth it.
Phil.