The best method of delivery for the world and history of an alternate timeline or parallel universe is to write documents and accounts framed as if they came from that world itself. It takes 'writing about a world,' which has an air of fiction about it that presupposes every sentence with "pretend this is true," to the next level: 'writing from the world,' wherein the reality of the world unto itself is foregrounded.
An example would be a historian's account of certain events, or scraps of journals compiled by court officials, or even journeymen's accounts as they traveled the countryside or city. This approach requires both research and creativity, whereas a regular design document would purely be facts strung together. The language of the world is also explored, but even more than that, it allows the mindset of people from that world-- and by extension, the fictional world itself-- to come alive.
Structurally, each snippet of narrative that delves into the world of Romahedron is a short story. At its core, it tells some piece of information about the world. Whether it can be a standalone story or not depends on each specific story itself. In addition to prose, or perhaps even the occasional piece of poetry from some homeless poet wandering the streets, images are used to add flavor to all the accounts. Stories could even be inspired by famous paintings of the time period, reinterpreted to fit the alternate history.
In summary, the execution of the world narrative from Romahedron is as much an exercise in creativity as it is in pragmatism. Details explored in what is written add depth and richness to the IP, both factual and flavorful. By adding a new dimension to the game, New Rome is freed from the constraints of the game space and enabled to roam free in the minds of players.