No unroll sorry. This function is not available yet. I don't know when it will be. You may be able to use Kangaroo (I'm not sure), but it won't be similar to the Unroll in Rhino.
Your post got me thinking, so I took a stab at it myself. I just posted the files on my blog; take a look and see if it does what you're looking for. It works well for portions of cones, and I haven't tested it a whole lot further than that.