New to bonsai and i just picked up this hawaiian umbrella from someone who didnt know much about it. Some question i have are do the roots look healthy and what type of fertilizer if any should i use?

This lokos like a mess. Is the plant healthy?

I would remove the rocks, which are partially glued together. Then look at the soil.
The plant should be planted a bit deeper.

A full repot is best done in late spring, early summer for tropical plants. If you are heading into winter now, consider lifting this out of the current container. Take a container a size larger and fill te space with good quality potting soil, making sure you bury the roots as much as possible. Then wait for spring.

The bonsai looks pretty healthy. It is about 12 defrees here in Alaska right now but very warm in my homee. Would it be a good time to de a repot?