Sasha Trubetskoy is a “geography and data nerd” who makes data visualisations and maps. His Roman Roads project styles the Ancient Roman road network as modern transit maps.
That’s the full Empire, as of ca. 125 AD. Trubetskoy also made similar maps for Britain, Italy, Gaul and Iberia. I recommend clicking through and reading about the process, including how he developed a framework for choosing twenty colours at various levels of contrast and accessibility.