Ok, so you are using Sublime Text 2 and you can use Cmd-B to execute ruby code, but that ruby code won't be executed using under the environment dictated by the .rvmrc in the project which is a pity. The same goes for RSpec, where you usually want to use bundle exec rspec in addition to .rvmrc.
I'm going to talk first on how to get regular ruby + RVM from Sublime Text 2 and then I'll jump onto executing RSpec together with RVM and Bundler from Sublime Text 2.