Most of the rest of the world?
But I know perfectly well it is only now really being made more accessible.
I'll just be patient.
(I just saw a 5e D&D compatible product about Ethiopia and its mythologies, so the times are a changin'.)
Of Rome, as I am not too interested in much of the already trod stuff. I'd like to see some North African Rome stuff. I mean, ruined & colonized Carthage, the lingering impact of Egypt, Leptis Magna-Tripolitania, the humbling wonders of Malta, the mysteries of the Atlas mts and the Berbers therein, etc. there's so much to work with. However they -- a good 30%?, 40%? of the empire -- are so often reduced to footnotes & afterthoughts when talking about Rome.