Yes, Rhino has a direct export to RIB. You might want to grab the demo version first and give that a quick try to make sure it will work for you, but I expect it should be fine.

There's also a Rhino plugin called "RhinoMan" that might be useful, I think it is set up to make the RIB export better yet with stuff like assigning shaders, etc.. http://www.rhinoman.com

- Michael