The whole reason I brought this subject up is because I found that when trying to locate a 19.5" rim and a tire for a spare on our last motorhome, It wasn't easy. I live in a city of a half a million people and I could not locate a rim here locally. I ended up having to get a rim off of Ebay and a used simi truck tire locally for my spare which I ended up needing as I had a complete blow out up in the mountains.
I am also in the process of changing insurance carriers for our new rig. In my research I have read a lot of unhappy reviews of people thinking roadside service is going to take care of everything when having a blow out. Many people state that roadside service will come to you and change YOUR spare tire for you. If you don't have one, It sounds like you're screwed?
Is there anyone out there who didn't have a spare tire and roadside service was able to take care of you anyway? I think that it would have to be a situation where they are able to locate a tire, bring it out to you, take your bad tire off of the rim, and then mount the new tire on it. That doesn't sound like anything that would happen quickly but maybe I'm wrong?