just do your research. Some of the regular auto insurance plans that people talk about on here do providing TOWING service and much more. Some insurance plans only provide TOWING service which is not the same as a Roadside Assistance program. Some will do tire changes on your truck but not your trailer. Be sure you know what is covered.
think about different scenarios such as truck is broken down, will they tow truck and trailer or will trailer be left by side of the road? Two flat tires on trailer, will they bring and change the tires or only change the tires if you have the tires if you have two spares with you? These are the type of questions to ask now while buying a plan, not when you are sitting on the side of the highway.