Yet another query from a gardening newbie.

I've just dug out a heap of soil and assorted debris (quite possibly decent
compost which i've sifted roughly and spread) from the corner of my newly
inherited garden. The problem is that in order to level it i've had to
expose a fair amount of the roots of an elder tree which was buried in it
about 3 feet above ground level and has been rooting in it for years.

The tree, which hasn't been pruned or cared for for about 10 years i'd
guess, is looking a bit patchy but has enough life left in it to warrant
some TLC and is about 12 feet tall. My question is what should be done about
the substantial amount of roots that are now exposed? Should I leave them,
prune them or find a way of covering them over again?

The tree hasn't been pruned for years either. Advice please?

xiv