Some of these "glands"
go through the roof, but my favorites are the ones that can be mounted high on the side wall, wire entry facing down
, with the back aligned with the inside of a cabinet to enable a clean installation. It's easier to monitor and maintain a gland on the side wall than it is if it penetrates the roof.
As for dressing the wire with clips or mounts, if you choose to go with screw clips, these are what cable installers use
. Pre-drill and fill the hole with silicone or some other sealant, slather sealant on the threads, then install. Then slather with more sealant. Monitor and maintain as you would any other roof penetration...of which there are plenty on the roof of any RV. The hex heads on these cable clips enable fairly easy removal even if the heads are gooped up with sealant. This enables easy, regular roof maintenance under the cable by removing the clips from the roof, doing your roof work, then re-installing. If the cable is secured every 2' to 3' with these, it won't go anywhere from winds at highway speeds.
I used these to dress the cables from my solar panel on my rig.
One other option...less sure about this one. I have some industrial strength 2" Velcro
. I used it between my bag awning and the camper body to keep the bag from being lifted by the wind and slamming the camper body. This Velcro sticks to the bag (soft vinyl) VERY well, and sticks to the fiberglass body as if it's bolted on. And the Velcro itself is so powerful that it's very hard to pull it apart. Adhere one side to the roof and hold the cable to the roof with the other side. If it sticks to the roof well enough, it might just do the job.
Sealants are great...as is Eternabond Tape. But fasteners are fasteners, and despite looking pretty hard, I found no EXTERIOR GRADE adhesive cable clips...especially ones that will stick to a broad spectrum of roof surfaces and textures found on RVs. Stick to fiberglass? Sure...something smooth and hard might work. But most RV roofs are some sort of rubbery stuff.
Anyway...that's my 2 cents. Good luck with your project.