I actually love the concept of this game, and looks really well polished on top of that!
I have a feeling the second road type is not very useful however as I find the game quickly becomes essentially upgrading roads to ice on the areas that have the most tower coverage.
I like the idea that specific colored tanks cant be targeted by towers of that color but there isn't much way to abuse that mechanic with the tank spawns being random so on multi-lane maps you're sort of praying for RNG. Having ways to control and filter the flow would be fantastic imo.
Tower spawns being based on where the roads are also leads to wanting to place dummy roads in far away areas to reduce spawns in areas where they actually make a difference, which leads to a potential strategy of destroying and rebuilding roads to prevent towers from spawning on their path, which might and might not be intended strategy.
Overall a really creative idea that can lead to some crazy potential given enough time to cook!