roll down a hill like a log

[De'vID]> Can ron be used for people, such as in martial arts or gymnastics?

Yes, IF it means that the person is rolling haphazardly.

If the person is doing a somersault (rolling forwards or backwards in a reasonably controlled manner), the verb is Hay.

If the person is rolling down a hill as if he/she were a log, the verb is tetlh (related to the noun meaning "scroll," though it's not used for scrolls unless a scroll is rolling down a hill).