Who built the Roman aquaducts?
The Roman aquaducts were built for the most part by the Roman Army. These aquaducts are still considered a great feat of engineering by today's standards. The idea of 'public works' projects was used by Rome to keep the army busy when they weren't at war. The Roman mentality was that soldiers needed to be kept busy or else they might become lazy or think about something other than the greatness of Rome. The aquaducts served to supply Rome with fresh water which in turn kept water born diseases low. The Romans understood the importance of fresh water to their well being. However, the aquaducts also served as a sort of 'bridge' for the army. When the army approached a waterway that might impede their march, an aquaduct was constructed to allow the army to march over the waterway and at the same time provide another vein of fresh water to enter the city. The Romans' understanding of the importance of fresh water was one of a number of reasons why the Roman Empire grew and its' influences spread throughout Europe and the Near East.
Your question really answers itself. If the aquaducts were called Roman, then the Romans obviously built them. The Romans were known for being excellent engineers and their system for getting water to their population centers is still considered a great achievement today. The Roman probably used slave labor and a few paid laborers to do the physical work but Roman engineering was definitely responsible for the design of the system.