Nebari on Chinese elm

Hi there, I am hoping to get some help developing the nebari on my Chinese elm. At the moment, the nebari have no bark whatsoever and I am wondering if this is something that will develop overtime, or if I should just cover the roots to prevent them from getting too dry (I live in Colorado). My hope is that exposing them, as they are in the attached photo will aid in this process, but maybe that’s not something elms will do.

I can take quite a while for bark to develop on roots. Keep them buried if you want them to thicken, expose them when you want them to bark up.

Awesome! Thank you so much for the help here!