If the plant has lost all its roots due to root rot, I would recommend the following:
1. Cut away all the dead roots.
2. Repot the plant into new potting mix.
3. Place the plant in a shaded area with moderate humidity.
4. Do not water the plant until you see new roots growing. You can mist the leaves every now and then too cool it down, but it will not make use of any water inside the pot.