What is scriptable with “command lines” is whatever you could normally do with Rhino commands. But materials will be difficult. You can get to:
Material Library Color GlossColor GlossFinish Transparency TextureMap TransparencyMap BumpMap EnvironmentMap Match
-Properties Material Object
but if you try to get to “Library” it goes nowhere… As far as I can tell, getting a material from a library is not possible (even with normal Rhino commands), so I don’t think you have much hope here.
If you have a blank file pre-set up with materials, then it becomes more possible using RhinoCommon - you can first import the file, which will import the materials… If you have made sure that the materials have unique names - and that nobody creates new materials in the file with the same name - you can dive into the material table and grab the name, find its material index and assign that to the object. It’s not all that simple, though…
Dealing with scripting and materials in Rhino is probably one of the poorer experiences I have had on recent projects… I wish I had better things to say about it… Maybe I’m just too dense to understand it all.
From what I understood, the only reliable way to deal with this is to use the RDK SDK.