Вы должны быть в состоянии сделать это:
map.resources :users, :has_many => :submissions
Который даст вам такие маршруты:
users GET /users(.:format) {:action=>"index", :controller=>"users"}
POST /users(.:format) {:action=>"create", :controller=>"users"}
new_user GET /users/new(.:format) {:action=>"new", :controller=>"users"}
edit_user GET /users/:id/edit(.:format) {:action=>"edit", :controller=>"users"}
user GET /users/:id(.:format) {:action=>"show", :controller=>"users"}
PUT /users/:id(.:format) {:action=>"update", :controller=>"users"}
DELETE /users/:id(.:format) {:action=>"destroy", :controller=>"users"}
user_submissions GET /users/:user_id/submissions(.:format) {:action=>"index", :controller=>"submissions"}
POST /users/:user_id/submissions(.:format) {:action=>"create", :controller=>"submissions"}
new_user_submission GET /users/:user_id/submissions/new(.:format) {:action=>"new", :controller=>"submissions"}
edit_user_submission GET /users/:user_id/submissions/:id/edit(.:format) {:action=>"edit", :controller=>"submissions"}
user_submission GET /users/:user_id/submissions/:id(.:format) {:action=>"show", :controller=>"submissions"}
PUT /users/:user_id/submissions/:id(.:format) {:action=>"update", :controller=>"submissions"}
DELETE /users/:user_id/submissions/:id(.:format) {:action=>"destroy", :controller=>"submissions"}