Roofing (Cantonment)

1/4 osb or plywood that is a grade meant for outside. I have to replace my rv roof. I've already got the tpo and the insulation. I honestly have no idea what I'm doing but I know it's delnaninated from what I've read. It's literally just falls apart when I touch it. I also have to get glue and tpo cleaner to prep the tpo. I'm far off from being able to even start demo. The wood has been a major set back.