The real question for you to answer (or think about) is, "What am I trying to accomplish with my solar?"
Are you just trying to trickle charge your batteries while the RV is in storage? Or are you trying to have a modest amount of solar for occasional 2-3 day boondocking outings? Or are you trying to "live off the grid" for extended periods of time?
How many house batteries do you have? How many amp hours?
Do you have any idea how many amp hours you typically use in a 24hr period when camping? Does your rig have a battery monitor so you can easily know what your power needs look like? (if not, they are VERY handy)
What sort of refrigerator do you have? Does it run on propane when not connected to AC power? Or does it run purely off 12v? If you have a 12v non-propane refrigerator, you will need more batteries (AHs) and more solar if you want to camp unplugged.
Does your rig have a generator? That helps a lot.
If we assume you have 1 or 2 house batteries and you are a typical "weekend warrior" RVer that just wants to be able to boondock without electrical hookups for 2-5 days at a time and you have a generator, then you don't really NEED solar. BUT, solar is very nice to have as it keeps your batteries charged up most of the time (in storage or camping) and allows you to camp while not having to use your generator much at all (likely). Camping often means being out in nature where peace and quiet are enjoyable features (and not hearing a generator running all the time is better).
A simple rule of thumb if you want to be able to camp without being connected to power... For each 12v battery you have, you want 100-200w of solar panels. If you have two 6v GC batteries, you would want 200-300w of solar.
The general system components include:
Panels on roof --- connected to a solar charge controller --- connected to your batteries. You will want a resettable fuse/breaker in between each.
PWM solar charge controllers are less expensive.
MPPT solar charge controllers will give you 20-25% more charging for a given amount of solar panels on your roof.
Let us know if you have more questions.