Thanks for the replies.
@mikeynags Those junction boxes look nice, I'm just thinking I might want to stick to generic junction or gang boxes from Home Depot, Lowes, etc. that take generic covers since I will be upgrading my cameras every 2-3 years and don't necessarily want to stick with one brand - I might do Hikvision, Dahua, Bosch, Axis, etc, so I want a generic standard box so that 15 years from now I can still just get a new standard cover plate for and drill a few holes in the cover plate that line up with the screw mounts of the camera. Do you think this makes sense in this situation?
@tech_junkie Thank you for the idea on using the vents to help fish the cable into the attic - I indeed do have vents within about 2 feet over where I want to mount the cameras. The attic space is extremely tight as the roof is at a 2- degree angle, so I've been thinking about how to get the cable far enough back into the attic where I can reach it, and without bumping my head on a roofing nail. Also, without a junction box, what do you do about swapping the cameras out for upgrades every couple of years? In about 20 years with different models of cameras and different mounting holes, that would be a lot of damage to the building.