What RV do you have? I am not aware of any manufacturer that paints their roof. If it is not a rubber roof, it would likely be gel coated fiberglass. Either will streak your coach if they are not kept clean and/or have oxidized with age. Did a prior owner paint the roof?
If you are referring to a film made by 3M that you stick on your vehicle, IMO it is not worth the money and will look horrible when it ages and gets mold. I am in the process now of removing the 3M clean film from my coach and would never have it again.
Perhaps you are referring to something else.