Roofing material for patio deck floor

I have an unusual situation where the patio deck floor on the second floor also serves as the roof for the bedroom on the first floor. There is a white vinyl material on the deck now, that has already had a crack that leaked onto the ceiling of the first floor bedroom, and we know the wood beams underneath have rotted. In deciding how to recover this area, we are in a quandry. Are there any other materials besides tile or plywood/waterproof membrane that can be used as an effective covering over the replacement wood beams? Thanks for any assistance.