Without the government, who will build the roads?
This is a classic question with an easy answer: People who want to build roads would build the roads.
Someone thinks a road is needed, talks to the community to see if others agree, and then those with skill and interest go out and do it. Or maybe there is a collective who contributes to the community by building and maintaining roads.
Here’s a great example of this in action: https://www.huffpost.com/entry/anarchists-fixing-potholes-portland_n_58caaa7be4b0ec9d29d9575b