I would hold the dealership accountable, if the spec sheet on your purchase agreement stated it has 15" tires and it came with 14" that is unacceptable. Roadmaster should be going to bat on your behalf with this issue, otherwise I would recommend a complaint to the Better Business Bureau
. Unfortunatly this is the only way they will take a customer seriously.
If I bought a new VW Jetta and it was supposed to come with 18" rims but the factory sent the car with 17" who the hell would agree that it is ok for the dealership to say, too bad we cannot guarantee what the manufacture sends us????