For a walk-through to setting this up, check out this blog post:
Bodacious/FacbookConnectWithRubyMotion
A sample app showing how to set up a RubyMotion app to use the Facebook iOS SDK 3.1
Ruby
A sample app showing how to set up a RubyMotion app to use the Facebook iOS SDK 3.1
Ruby
For a walk-through to setting this up, check out this blog post: