Roman Empire means in the bible: The Roman Empire, in the apostolic age, was the only great power in the world. This included all that was between the Euphrates and the Danube, Rhine, Atlantic, and Sahara desert. In 63 B.C. Pompey took Jerusalem as a client and 6 Judea, at the expulsion of Archelaus A.D., was made a Roman prefect. Caesar provides a listing of all the Emperors of the New Testament period, along with their accesions dates. See also the Appendix for Bible Chronology.
(in Bible Dictionary)