Q.Bare Areas Under Trees
I have 4 trees, 2 maple and 2 pin oak, approximately 20+ feet tall that are growing close together, thus creating a large shaded area. Nothing is growing in this area, other than a few sparse weeds. The roots on the trees have gradually risen up through the ground. I have been considering laying down a layer of soil a few inches thick over the area and up to, but not covering, the roots and then planting a shade ground cover. My concern is keeping the trees healthy – what do you suggest?

Certified GKH Gardening Expert
In order to keep the trees healthy, you do not want to cover the roots (which it sounds like you knew already), but you can fill in around them a bit. That would be fine.
This section of the site has some information on gardening in the shade. You can find some suggestions on what to grow in this section:
https://www.gardeningknowhow.com/shade