I was asked to paint and restore a deck an as I got to its roof ran into a lot of flashing failure in inspection I found that previous owner had masked a serious overall flashing and drip edge failure. I can repair the sheeting tails and flashing properly just lost lost on the drip edge. The roof rolls up at all sides with downspouts at the corners. The drip edge is a capon top of that roll. How do I replace and seal that on top of the roofing material or is a system that will fail again? And what is the determining factor in deciding replace or recoat on torch down itself (whole roof)?