A lot of these questions today.. Start by putting them in with crickets. So he will see them as food. For worms put them on the screen and let them climb up this creates the hunting activity. Um flies usually are a loved treat because they are a challenge. Grass hoppers that are safe for feeding I always put on my pothos plants. I also hand feed so anything in my hand he eats.
Good luck they can be stubborn
It's just not liking it and wants to hunt. Roaches, I never really release in the cage. I let crawl on the mesh in front of the Cham. Usually you can tell when it's hungry.
If this Cham is shy over all, it'll not eat anything anywhere in front of you