It seems like if the Romans already had mapped out the area that roads would be unnecessary.
The Roman road network was largely an expansion of pre-Roman trackways. The intended function is usually assumed to be military, but there are non-military roads so it seems they were not unconscious of the civic/economic benefits. They were important because they facilitated movement--modern consensus in Roman economic studies is shifting away from three marginalization of land routes in economic activity, so the roads played an important economic role.