When I worked for RCA Service, our CCTV outdoor runs were exposed on roofs and we had no particular issues. I believe the Belden RG-59 we used was UV rated. I know that the cable rarely caused any problems, but the splices and terminations did, despite our best efforts at weatherproofing.
At one plant we had as an account, one camera was on the very top of a storage tank (I hate heights) and another was mounted over a driveway out on a pole spanning two buildings....five stories up. The only way to get to that camera was to shimmy out on that pole in a harness.
On one memorable call, that camera and two others were out..I was not looking forward to having to go out on that pole..but I got lucky. The cameras were out because the power was out in a large portion of the building. Why?
Acid washdown on the fourth floor got into a very large MCC on the floor below..the resulting explosions killed one worker, seriously burned two others and shut down production for a few weeks. I saw the carnage in person, it was amazing how much damage was done.