Your Routes file will need to look something like this, assuming you already have a User resource:
YourApp::Application.routes.draw do
....
....
resources :user
get ":id" => "users#show", :as => 'root_user'
end
The very last line - and it must be last, so it doesn't override other urls in your application - manually creates a path that should work. You can also reference it using 'root_user_path' in your code to create the links.