You can randomize color, but this doesn't apply to the material does it? I use the randomize color option all the time. It would really nice if they include the roofing materials in this.
Agreed, but it's better then one common color.
If you want, you can create a Style Rule that randomizes the roof material and limits it to just the materials you want. I'm working on a blog post that should be done this evening that explains Style Rules. Watch for it at civil3dplus.wordpress.com