Should it be Miles of Roads or Miles of Road
For words that are both countable and non-countable, I would use the plural for unitless numbers expressing multitude, and the singular for physical quantities with a unit.
- There are dozens of roads leading to Rome.
- The town has twenty miles of road to maintain.
- The barrel contains tens of thousands of grains. (I meant grain as a seed, not as a unit, but the sentence is correct for both interpretations.)
- It takes several pounds of grain to produce one pound of meat.