Two thoughts. If the roof deck is sound, where roof material is peeled back it will have to be rebounded to deck. If deck is in bad condition, it should be replaced as wood will continue to deteriorate. Also if deck is bad you could have some bad structural members below too.
I have worked on two trailer roofs. One I had to replace the entire deck and roofing material due to many small leaks and deteriorated deck. On the other I had to replace a portion of the deck and structural members below, ceiling panels and wall panels, plus wall framing in wall due to migration of leak causing damage
