The Roman aqueducts were large water supply systems delivering water for public health usage. However Little is known on the hydraulic design of the aqueducts. The Roman engineers, contemporary of Hero of Alexandria, had a strong expertise and experience in hydraulic engineering. Several regulations basins were found along the aqueducts. It is proposed that the operation was based upon adynamic regulation principle. Associated issues are discussed. Two types of major hydraulic structures were also built : dropshaft cascades and culverts. The hydraulic engineers who designed these structures have a sound knowledge and understanding of basic hydraulics. Who were they ? Although we do not know, the writer is impressed by fheir technical expertise. They knew more than modern hydraulic engineers.