Either local government where people voluntarily give their money ( Like state government or Local Council depending on which country you're in ) the trick is not forcing it on anyone and then also people can just get together and hire a crew to build it or you could do corporate sponsorship, since advertising is already used a lot on roads why not use that revenue to support the building of them? There are of course more direct methods like toll roads and frankly if you're going to bitch about that sort of thing then you're a cheap skate because I'd rather pay for it on a voluntary basis than be forced to pay for it or go to jail.

The trick is not forcing anyone to pay for it, you do that and you'll have a lot less resentment about building infrastructure and free healthcare, you might even have people going out of their way to support it like with a charity, oh yeah as long as it's run properly I have nothing against charities either, just so many of them are corrupt now and take a large cut of what's donated to them. It's only natural that when you threaten people with violence if they resist that people start hating the idea of giving money to the people threatening them.

Take Sean's Outpost as a living example of what can be done in a voluntary society as well people are quite happy to give that charity Bitcoin and yet according to your logic, if there were no taxes nobody would build any roads, yet why is somebody who isn't automatically being paid for it just taking Bitcoins and going around helping out homeless people?

Oh and do I have to point out the internet as a world wide source of learning? These days even with a pretty cheap internet connection that doesn't work very well you can do a damn lot of searching if you want to try learning something.