Can't get the cleave the Roman Empire choice

So. 2 Friends and I are playing in Europe. One of my Friends plays as the Slavic Empire, another one as Byzantine Empire and I play as Italian Empire. Through conqueror trait I unified Italy, expanded through most of Africa and took the lands and the title of Byzantine Empire (my friend). The idea is to restore the Roman Empire and get the hegemony to later split It in 2 and give the east to my friend). The problem is I'm not given any choice to convert hellenism or anything else. I simply restore the Roman Empire. I tried playing on my own, destroying the Italian Empire and doing It through the Byzantine Empire, nothing changed. Could It be because we're playing on easy or do we need any DLC (we don't have any)? I read something about Roads to Power, but the info about all this topic is almost non-existing.