Q.crepe myrtle tree
Although there is a raised mound around my crepe myrtle, some of the roots are exposed along the surface. Should these be covered with soil or mulch before winter sets in?
Here are some articles that will help you.
https://www.gardeningknowhow.com/ornamental/trees/tgen/exposed-tree-roots.htm
https://www.gardeningknowhow.com/ornamental/trees/crepe-myrtle/crepe-myrtle-root-system.htm
The root flare should be exposed and visible on a Crepe Myrtle and one of the most common problems with Crepe Myrtle is gardeners planting them too deeply.
You can cover the exposed roots but make sure you do not add to the root flare.
When working around the roots and the tree take care not to injure the tree. This could lead to disease and the loss of your tree.