The first step is to total the amount of power you wish to use on a daily basis. The amount of battery storage and solar charging revolves around your use.
For inverted 120V power, you can multiply the device's rated amperage by "10", to see what the 12V draw would be.
Portable panels are nice but it depends on how much you want to fuss with them. If you leave your RV for day excursions, will you leave the panel outside? Are you willing to move it so it faces the Sun? How much trouble will it be to move in and out when setting up camp?
Mounting onto the roof is not an issue, as is wind drag. Some folks use VHB tape to mount the panel brackets--no screws needed but that only adheres to the roof surface, not a good thing with an EPDM roof. Screws with sealant is the more common mounting scheme and nearly all report sturdy mounting with no leaks.
My solar system is similar to lawrosa's---one big panel , MPPT controller, and a 1000W inverter. I have 300 AH of battery storage. I run a 120V fridge and 120V entertainment devices, along with the other 12V items.
If you don't have a battery disconnect switch between your new batteries and the parasitic loads of your RV, I'd suggest to install one. The circuit boards, alarms, and radio memory will combine to draw down your batteries quickly.
