How to import component into another root component in Angular 2

You should declare it with declarations array(meta property) of @NgModule as shown below (RC5 and later),

import {CoursesComponent} from './courses.component';

@NgModule({
  imports:      [ BrowserModule],
  declarations: [ AppComponent,CoursesComponent],  //<----here
  providers:    [],      
  bootstrap:    [ AppComponent ]
})