rvluv, from my recent research on this topic, many experienced RV'ers here have Progressive insurance on their rigs. It looked to be the least expensive coverage for RV's compared to other companies, even though Progressive's auto policies are not necessarily the same way. There were also several positive experiences about filing claims, regarding service speed and few-questions-asked payouts.
Now roadside assistance is another animal, I'm not sure if Progressive offers it and it's certainly something you'd want on a large RV.