While you can use this.context.router to navigate around, many apps want to be able to navigate outside of their components. They can do that with the history the app gives to Router.
// your main file that renders a Router
import { Router, browserHistory } from 'react-router'
import routes from './app/routes'
render(<Router history={browserHistory} routes={routes}/>, el)// somewhere like a redux/flux action file:
import { browserHistory } from 'react-router'
browserHistory.push('/some/path')