In MapPoint, you can create routes from any point on the map - a street address, an intersection, one of the 800,000 or so points of interest included in the map, or just a random pushpin location.
Your request for maps of the Roman Empire is an interesting one. I assume Microsoft will prioritize that below adding coverage for Asia, Australia/New Zealand, South America and Africa. They may also find it hard to get the right data from NavTech on the road network...
