I'm sure your bird is like most parrots, they like what they like. You will probably just have to experiment to see how he prefers them. My IRN will eat them just about any way. Cooked, raw, small pieces, larger chunks. He's not picky.
Your ringneck may be a little more picky. I will buy bags of frozen vegetables, heat them up a little (don't serve them hot) and watch what he goes for. He loves hot peppers, green, red, yellow and orange bell peppers, carrots (raw or cooked), corn, peas, broccoli, etc. Here is P.J. eating in my office right now. He is eating a whole edamame- it's sort of like a mini foraging toy that is edible. Good luck in figuring your bird out, it's a fun process isn't it?

