The Roman Empire (Latin: imperium romanum) was the largest empire of the ancient world. Its capital was Rome, and its empire was based on the Mediterranean. The Empire dates from 27 BC, when Octavian became the Emperor, Augustus.The empire was the third stage of Ancient Rome. Rome was first ruled by Roman kings, then by the Roman Republic, then by an emperor.Many modern lands were once part of the Roman Empire, including Britain (not Scotland), Spain, Portugal, France, Italy, Greece, Turkey, Germany, Egypt, and the north coast of Africa.The main language of the Roman Empire was Latin; Greek was an important secondary language.any modern lands were once part of the Roman Empire, including Britain (not Scotland), Spain, Portugal, France, Italy, Greece, Turkey, Germany, Egypt, and the north coast of Africa. The main language of the Roman Empire was Latin; Greek was an important secondary language.