The system of governance and the community are in competition for resources. When the system has more power, the available resources are allocated into the growth of the system. When the community has more power, the available resources are allocated to the welfare of the community. Decentralization removes power from the system, and adds it to the community.
The general problem with socializing things is that in practice costs are socialized, and benefits are privatized. A lack of effective checks and balances will mean that the fox is always hired to guard the henhouse.
Roads are NOT going to be built in any kind of efficient way without public funding.
I'm glad you emphasized that because otherwise I would have thought it wasn't true. I've seen the road work around here, and it's pretty clear that the ratio of supervisors to workers is 4:1, that roads are rebuilt when they are in perfectly good condition (presumably because someone's brother-in-law owns the tar & sand company), that roads are built in places where nobody wants them, that roads are not built in places where people want them, that millions are spent on roads, but no one can be chuffed to spend a couple thousand on a traffic light until at least 4 or 5 people get killed at a given intersection, that the competence of traffic planning falls somewhere between the Riddler and the Joker. Why? Because there's no competition which demands excellence, or even a slight whiff of competence.
the community seems to have decided that it wants more roads.... b/c they see that as the solution to the issue of having more people in the area.
If it works like it works around here, the community has precious little to do with it. County commissioners hire managers who decide what happens. There's no real community participation and no real accountability for what they do. Certainly the system has done what you say in the example you reference, but whether the community has done so is a separate question.