Forming Roman Empire as unreformed pagan

You can have a norse Roman Empire, however you can't change back immediately. This shouldn't figure too big a problem though.

A detailed step-by-step guide of what I did:

1. I took the Byzantine Empire by kidnapping a close relative of the Baselius and got a kid with her (kinky!)
2. Conquered the required Duchies
3. Moved my Capital to a Christian County to convert
4. Gave my heir the title of Fylkyr (the religious head of reformed norse)
5. Switched to Christian
6. Formed Rome
7. 'Lost' to a Tyranny rebellion so my (still norse) heir takes over. (you could also just wait for your current ruler to die, but that might take a while)

Whether you keep the title of Augustus I can't explicitely remember, but I don't see why not. I will load up the safe when getting home to check.

Note: I do not know whether any DLCs are required for this as I always play with all enabled, and it was well over 2 years that I did this myself, so they might have changed it (which I doubt however)

EDIT: The DLCs needed for this: Legacy of Rome to form Rome (obviously), Old Gods to play as Pagan (thanks to @RossRidge for pointing this out) and Sons of Abraham so you can move your capital.