We had a Live Oak Removed over 10 years ago and now a fungus is coming up. We have been told it is from the left over roots of the tree. These round glistening musroom type growths are really nasty. What to do?

Sounds like normal rot to me. It's a natural thing for the remaining roots and stump to decompose. You don't have to do anything and they will go away in a few days usually.

Wood needs fungus to decompose. Like it or not it is necessary.