The statement that most accurately describes the size of the Roman Empire at its greatest extent is:
It stretched from the Atlantic Ocean to the Red Sea.
At its peak, the Roman Empire encompassed large parts of Europe, North Africa, and the Near East, stretching from the western regions of Europe (including modern-day Spain and Portugal) to the eastern Mediterranean and the borders of the Arabian Peninsula, including territories that reached to the Red Sea. However, it did not cover all of Africa, all of Asia, or all of Central and Eastern Europe.