i can't find a way to add sp dynamically bau use this method could help you:
DataContext.Context.ExecuteStoreQuery<ilist><roles>>("seleci id from...",param object params);</roles></ilist>
means that the return value is a list of Roles(a table in my database) entity, in entry method you set the query script as a script, and at least add params as
to this method!
sorry this is not the solution that you want, but maybe this can help you a little!