To repeat most of what has been said.
For boondocking more than a few days "some" solar is mandatory. Solar will finish the last 20% of charge, to bring it to 100%. This last stage is slow, you don't want to run generator that long.
It's important to charge it very close to 100% on most days. 85-90% is not good enough. There no way to make this last stage faster. Upgrading the cable will only make the first 80% faster - and voltages will be more correct with thicker/shorter cable. Charger or converter still needs to be adjustable 3-stage.
Big solar on the roof with adequate size battery could run the whole RV without generator, except for air conditioner. Can be difficult to design and install for some people.
Small solar on the roof is about same easy or same difficult as a big one. You need to know what you are doing.
The easiest way to add a small solar is to go portable. Buy 100-120W panel, 10A controller, 20-30ft of cable, and lean the panel against trailer tongue or prop on a milk crate. Or buy a portable 100W "suitcase" by Renogy, will cost more than DIY but everything is included, convenient option for those who don't know how. It will not run the whole rig, but will do those last 15-20% - silently.
Another source for solar:
http://www.solarblvd.com/.
