Roadside Assistance programs vary, but the main point of them is to help you if you call in with a request while on the road. The typical program covers towing, locksmith, battery jump-start, fuel delivery, and flat tire change. Some services include winching which means they will help pull your car out of a roadside ditch.
This service is usually only a few extra dollars a month, but you will need to be careful not to use it to often. Once a quarter would be fine, but if you are using roadside assistance multiple times a month, your insurance company will raise your insurance rate to compensate for how often you use it.
Some find it better to purchase roadside assistance from a motor club such as AAA. Motor clubs are usually more expensive, but offer more service as well.