What Libertarians are pushing for is an end to taxation with voluntary funding of endowments for common services. At the same time private or privately run public entities should be fully legalized.
In looking at the roads the question is movimng towards endowment funding and legalizing private alternatives. Tolls may be a middle step in some cases but truckers have a point: The roads should have been fully funded in the first place, and gas taxes for roads get diverted to other projects.
GOOGLE Libertarian International Organization for some interesting perspectives.