Complex sentence: The most notable engineers of ancient times were the Romans and Chinese, who constructed huge siege-machines (catapults, battering rams and siege towers) and were responsible for constructing fortified wooden camps and paved roads for their legions.
Split into simpler sentences: The most notable engineers of ancient times were the Romans and Chinese, who constructed huge siege-machines (catapults, battering rams and siege towers). The Romans were responsible for constructing fortified wooden camps and paved roads for their legions.