Simple question on routing, I am unable to find a component in app.component.ts which is from another module

@rapropos
Forgive about my phrase, if you do not understand.
I have created register-user module like BrowserModule, MomentModule or any other module which we import usually in app.module.ts.
This module will have several small components like login, sign up, forgot password, etc.
I need a user to start with login screen first which is defined in register-user. This start screen we mention in app.component.ts file.
So if I import a module in app.module.ts & in app.component.ts file, how I will access login screen?
Do we need to define routing in register-user module like explained in the link below:
New angular2 router support in ionic