Wow! Same thing here...this morning I was checking the roots of my mtssa, and ! Looks exactly like roots in your pictures--a great big mass of tangled roots without a speck of soil. I had trouble dealing with orchids with none or too little roots, but the opposite?
With so many roots, I can't imagine how to repot it (correctly) without damaging some of the roots. Well, try your best to get the old medium out...some roots may be hurt, but it's better than having the old medium spoil and cause rots.