Read the policy or the prospective policy first before buying anything. Roadside assistance through vehicle insurance may not be sufficient or appropriate for RVs. Some roadside assistance might even exclude RVs, so reading the fine print is required.
I think the high points are that you will want to make sure that whatever policy you get provides the services you think are necessary should you get stranded someplace with the RV. The roadside assistance needs to not just provide a tow to the nearest mechanic, but to one that can actually deal with your vehicle type, this is especially important for folks with DP coaches and gas class As.