The term 'Roman Peace' is a reference to the Pax Romana, a period of relative peace and stability in the Roman Empire that lasted from 27 BC to 180 AD. The Latin word for peace is 'pax', which is the solution to the crossword clue with three letters. The Pax Romana was a time of great prosperity and expansion for the Roman Empire, and it allowed for the spread of Roman culture and law throughout the Mediterranean region.