Defining routes file(s) in the Route Service Provider - http://slashnode.com/definitive-laravel-4-to-laravel-5-migration-guide/

RouteServiceProvider.php

<?php namespace App\Providers;

use Illuminate\Routing\Router;
use Illuminate\Foundation\Support\Providers\RouteServiceProvider as ServiceProvider;

class RouteServiceProvider extends ServiceProvider 
{
    /** ... etc */
    public function map(Router $router)
    {
        $router->group(['namespace' => $this->namespace], function($router)
        {
            require app_path('Http/routes.php');
        });
    }
}