Around here when a roof is removed (assuming typical asphalt), it takes a couple of hours with the push-scraper tools, and the asphalt landing in the dumpster, if not the lawn and foundation plants.
I would think to remove a roof with any chance of reusability would take many painstaking days. And, even then, you'd wind up with nailhole leakpoints in every shingle.
Probably a metal roof. They are very popular now, and the panels definitely are reusable.