The Roman Empire is a titular Empire title.
With 
Legacy of Rome expansion, it is possible, as Emperor of the Byzantine Empire, to restore the Roman Empire by controlling key duchies of the old empire. The Byzantine Empire must also be your primary title. Restoring Rome has the following effects:
- The ruler will receive the nickname "the Glorious".
- Roman emperors are automatically given the
trait, which grants +10 vassal opinion and +0.5 monthly prestige. This can stack with the +5 opinion modifier from being 
, and the +10 opinion modifier from rapidly accumulating 2000 prestige. - Any duchy considered rightfully part of the Roman Empire can be attacked using the "Imperial Reconquest" CB (Muslims cannot be attacked using this CB; you'll have to risk holy war).
- The de jure capital moves from Constantinople to Rome.
With 
Holy Fury activated, Christian emperors of Greek, Italian, or Roman culture have the option to restore the old Imperial religion Hellenism through a series of events.