Very interesting! I can see those being the major roads (Roman 'highways', lets say). In addition, there are probably quite few minor roads connecting settlements and Vicii, as have been identified on the right bank of the Rhine, for example.
Very cool. When I was in Egypt last time I actually walked on the remnants of an old roman road that went from el-Ashmunein to Minya (central Egypt). I visited the temple of Thoth in el-Ashmunein (known in ancient times as Hermopolis Magna) and then headed north on the road. Went past a very cool late roman/byzantine fortress at a bend in the Nile. It was used as a toll collecting place for ships going up and down the river. Now it is surrounded by mud-brick houses belonging to the local farmers. When they saw me walking down the old road some of the villagers came out of their homes with tea, very refreshing!