The last guy who came out to look at doing my barn roof repair said the ladder slid out from under him on his last roofing job. He shattered his leg, ankle and foot. They put a rod in his leg along with a bunch of screws. He said the doctors told him one more fall could mean they'd have to amputate, and he has $130k of unpaid medical bills. I won't hire him because even I worry one misstep could send him tumbling and cause him to lose his leg.
One thing that a roofing crew does that makes it safer is they have a guy up near the peak to screw down the roof. They have a guy lower at the eve to screw it down in that area. They don't have to scramble up and down like a single person would. Plus they have helpers on the ground cutting the metal and feeding it to them so they minimize having to walk on the roof.
Metal is different to install than shingles, especially for one person trying to handle long sheets that want to slide off a roof pitch like that before it can get screwed down.