It wasn't a mad Nazi scientist, it was a 19th century German tax collector who needed something to scare people into coughing up their due taxes who first created Dobermanns. Rottweilers are a separate breed (and look somewhat like the Wardogs in RTW), and apparently their origins do go back as far as the Roman Empire, so it would make sense if the models were based on them. Apparently today's Rottweilers are the descendants of cattle-herding dogs used by the Roman Army, and in particular of those military dogs stationed in what is now Rottweil, Germany.