I do not know if this is possible or not, but it would be cool if you could see traveler on the roads. Some road will be more busy then others. Exaple a road in Mirkwood would not be busy, or have nobody on it at all. While in Gondor the roads will be filled with citzens and soilders. Also travleing traders' will spawn on the road. It will make more sense then to have one spawn in the middle of Middle Earth.
Roads will also make a little easier to get alliment. If there is a wood elf nearby and you kill a orc you will get a alliment for the Woodland Realm. It would be cool if orcs have a higher spawning rate near roads.
Lastly it just make Middle Earth more alive, give it a use, so it is not just a decoration. I hope you liked my idea, and thank you for reading this.