Never seen it. Do have some ideas on how you can judge whether something would make a good RPG.
First, if you are just asking, 'Could you set a D&D game (loosely) in real world antiquity?", the answer is certainly "Yes." But that's a really broad question and it doesn't cover the case of 'Can I translate this story into an RPG'?
1) Is the story episodic? One of the problems you run into in some stories is that the only viable story in the campaign world is the one being told in the story. Don't assume that a setting driven story necessarily makes a good RPG. In particular, 'end of the world' story settings make difficult transitions because the writer probably told the one big end of the world story for that setting and all you are doing is trying (and failing) to recreate it. What you really want for an RPG is a collection of short stories, each with thier own twist (and perhaps even its own characters), that are loosely linked together by the framework of the setting. Then all you have to do is think up your own short stories that are in the mode of the original ones.
2) Is it character driven? If much of the attraction of the story is the interesting characters and how they relate to each other, then forget about it. You want at most characters that are iconic because of what they can do, not because of who they are. Slightly shallow characters are probably better than fully fleshed ones because then you know that the story will work with someone else in the role. You want story driven worlds. A character driven world puts alot of burden on your PCs to drive thier own story, and not every group is up to that. In any event, even if your PCs can handle a character driven story, it will be a completely different one than the one you are trying to capture. Beware 'soap opera' style stories where each scene generally involves 1 main character talking to 1 main character, then they part and 1 main character talks to another different main character, and so forth. PnP RPGs generally don't work with this intimate sort of framework.
3) Is it ensemble? If there is one central hero on stage almost all the time or worse yet, all the time, then forget about it. D&D is played in groups. Unless you can imagine the role of the hero replaced by a collection of heroes acting together, then you won't have a game. And in any event, if you can, it won't be the same sort of story. Beware the story about the one super cool hero. Some of them work as ensembles, and some of them don't.
My suspicion is that the Rome series is not episodic, its involves a single (in this case historical) story that you can't recreate when players have free will, and that it is told in a character driven way. So, my answer from complete ignorance is, "No, you couldn't."
But, you could set a story in ancient Rome involving a group doing deeds of daring.
Since they're wandering, but the empire is unfolding around them, it wouldn't be affected by "free will."
