Detail this asset from Unity Asset Store: Original Link
This is a paid asset, but now you can download Easy Roads Mesh Gen Free.
Easy Roads Mesh Gen v2020.1 (Latest version)
Easy Roads Mesh Gen v0.5
Create roads and rivers without the need of 3D modeling software!
Easy Roads Mesh Gen allows for very fast and easy creation of roads and rivers inside Unity. It has easy to use, simple and organized interface which improves the workflow.
Just drag the navigation points where you want them and the tool will do the rest. Pick your own texture and apply it on top. As of v2020.1 there is support for basic terrain morphing which greatly reduces the effort required for matching the generated mesh with the terrain.
The tool comes with a free to use road texture.
This version of the tool does not generate crossroads automatically.
If you are updating from an older version, make sure you switch the “Update mode” option to Automatic, this will greatly improve your editor performance while still allowing for realtime mesh update.