Do not confuse roadside assistance plans with an extended warranty. The roadside plans typically cover a tow, roadside flat repair and will even bring you out a few gallons of fuel, but will not cover the cost of a tire/rim. Extended warranties are really insurance policies to address specific problems and you need to read each one to know exactly what is covered. Since I don't have one I don't know if tire replacement (usually called roadside hazard on autos) is covered in any extended warranties, but my gut feeling is that are not. I'm sure others with direct experience with policies will chime in.
Lou
05 Travel Supreme Envoy