the argument I often hear from minarchist that you can get trapped in your private property by people owning the roads. But really, even if you end up with hundreds of people owning little bits of specific road and demanding you to pay each time this will end up being inefficient. Since the free market hates inefficiency you'll get all of those people forming some kind of union/agreement to set up one fare and then share the profit. The same thing can be done with other road owners. Also that's kind of the reason for owning road - so people can use it and it would be unreasonable to ban anyone from using it.
But I often say "who needs roads, when you cna have flying cars"