Solar panels can be either portable or fixed (i.e. mounted to a roof). Typically solar panels keep the batteries charged, and you use the batteries for your electricity needs.
Therefore, solar panels typically connect to the batteries.
Solar panels also need a charge controller. For really small panels this is mounted integral to the panel itself... for larger panels, they are a separate unit.
For the solar panels themselves, there are two predominant types: monocrystalline and polycrystalline. This term describes the physical configuration of the solar cells themselves, and the main thing though is monocrystalline tend to be a bit more efficient (more power per sq in). Monocrystalline tend to last longer as well, but they are more expensive. It's the old "you get what you pay for" thing.
Perhaps the best starter solution (but fairly low power) is something like a Renogy Suitcase RV Solar kit. It is fairly inexpensive (usually below $300), and as the name suggests, opens like a suitcase with mounting brackets to sit it on the ground with an angle to the sun. The panels for this system offers about 1,000sq in of solar cell surface.
100 Watt 12 Volt Portable Solar Suitcase | Renogy Solar
The Renogy kit I think used to be Polycrystalline, but I see now that they are Monocrystalline, which is a good thing.
For these panels, you simply connect it to the batteries. If you connect to the coach batteries, it will charge them... or if connected to the engine battery, it will charge it.
100W is not really a lot of power though. At peak (max sunlight), 100W will theoretically give you on the order of 8amps, which is not a bad charge rate for a 12V battery. However, unless you are in the bright Arizona noon-day sun, you may only see 1/3rd of that rate. The operative here is "your mileage may vary" when it comes to how much energy you will get out of your solar panels.
There are other suitcase portables that can give you up to around 200Watts.
If you are looking at something with a bit more power, say 400W or less, then many RV owners could install it themselves, especially if they have no need for an inverter, but simply want to keep batteries charged.
You would have to map out the RV roof so you put the panel mounting stanchions on the roof ribs (they could easily blow off the roof when you approach 60mph if you blindly screw them into the roof), finding a suitable location to run the wiring from the roof, a location of the charge controller, and connection to the batteries.
You can also buy these from Renogy as well as other sources.
But if you need appreciably more solar capacity (say you want to run an inverter so you can run A/C), then it gets quite complicated as you are then adding an inverter and additional batteries.
If you are looking at such a high power system, I'd recommend a specialist, as you can make some very expensive mistakes if you are not buying the right components. In this instance, I would not go to a general purpose RV dealer, I'd go to someone that specializes in RV solar systems.