you should extend the devise config here. I know in some tutorials they do it like this but cleaner solution is like here: 
http://deepakrip007.wordpress.com/2013/10/28/facebook-connect-integration-using-devise-and-omniauth-in-rails-app/
check step 10. you have just 1 line in the routes:
```
devise_for :users, :controllers => { : omniauth_callbacks => "omniauth_callbacks" }
```