I'm not clear on who "owns" roads (i.e., which Civ pays for them and is able to destroy them with Workers) in a few scenarios: 1. I build a road in an unclaimed/neutral tile which another Civ later takes over. 2. I take over another Civ's city. Its land has several roads in it. 3. I build a road in a City-State to fulfill a road quest, and then I lose Friendly status or they are taken over. (and feel free to explicate any other odd cases I can't think of right now.) I know Open Borders with a neighboring Civ allows you to make Trade Routes through roads in their territory in certain circumstances, but I'm not super sure on the details.