Adding soil

Roots will grow anywhere water is present and not hit by some level of light -- if hit by light it will differentiate into stem and no longer be able uptake water. superficial roots are not ideal. usually means some bad irrigation habits or possible overgrown relative to pot size etc... not positive cuases in general. They will be susceptible to erosion and such as you water.. once exposed they are just "stem" with no root capabilities in a short time. Lots of stem doing nothing isn't a net positive though not the end of teh world either, of course. just something to avoid. Adding a little on top to cover up superficial roots is probably a net positive, though. It will prevent those exposed roots from turning into just "stem" material. make sure you always water entire substrate with no dry pockets.. minimal runoff for soil and at least 10% in soilless context. this helps roots drive down instead of growing toward surface. erosion and compacting over time will occur. roots may get exposed up top and this is a great time to add a little substrate if you can, sure. if you get a lot of superficial roots, consider some habit changes to how you water.