Nellisir said:"Imperial Rome", part of Green Ronin's Mythic Vistas line, is coming out in a few months.
I've heard that too, although I haven't seen anything on Green Ronin's site about it yet. Maybe the cover artist is slow (he said groundlessly).
I'm running a campaign set on a pseudo-Earth during the Roman Republic (not quite what you're asking about), and it's going pretty well. I will say the obvious, though: unless you're drastically cutting down the magic & demihumans & monsters from "standard" D&D, any Roman setting (like any historical setting) will rapidly mutate into its own weird fantasy setting. Once I accepted this, my world-building got a lot more fun, and now I've been going back through my campaign's timeline, injecting historical events with D&Disms ("Hannibal crossing the alps to invade Rome with elephants... naah... why not Hannibal crossing the alps with DRAGONS?!?!")

Jason