Dammit roofers, wear your safety harness, air traffic is counting on you!
When my total-roof tear-off was done around 8 years ago those Mexicans didn't wear any harnesses. They looked as unconcerned as squirrels, they were used to it. AFAIK, none of them fell, it was a big crew, just one of around 6 (I think) working for a local roofing company. I've been up on my roof a zillion times, I'm used to it. If you're not used to it, it's very scary, but you can gain confidence, you adopt practices, hand-holds. But doing roof work is another matter, you get tired, there's debris, there's a ton of work to do, you have other guys around you, there can be the additional stress of hot tar fumes, the weather can be very challenging... hot, cold, wet, windy. It's tough work, dangerous.
The workers seem to have done a pretty good job (still no leaks AFAIK), but the guy(s) who nailed on the shingles (with a power-nailer) rushed and I could see the heads under a lot of the shingles (a no-no). I made them replace all the shingles (that I could find) that were improperly nailed, I'd go up there after they left and inspect. Good thing I wasn't afraid to ramble around on my roof. They also failed to put double underlayment on a section not steep enough to warrant single underlayment. I made them redo that too! If I had it to do again, I'd hire a company with just one crew, where the owner was the crew chief. A company with a bunch of crews with rotating staff on a day to day basis likely doesn't have adequate supervision going on.