Gently work the plant out of it's pot and carefully remove the sphagnum moss. Set the plant in a pot of tepid water and let it soak for 10 or 15 minutes. The roots that plump up after soaking are live. roots that are squishy are dieing and need to be cut off, roots that remain shriveled after soaking are dead and need cut off. You can leave the plant without repotting for a few days (weeks) as long as you soak the roots for 10 or 15 every day. I suggest you repot in a bark mix.