gistfile1.php

    public function index()
    {
        $this->paginate = [
            'contain' => ['Roles']
        ];
        
        $this->set('users', $this->paginate($this->Users));
        $this->set('_serialize', ['users']);
    }
    
 # Error: SQLSTATE[42S22]: Column not found: 1054 Unknown column 'Roles.roles_id' in 'on clause' 
 
 #
 # UserTable is:
 #
 <?php
namespace App\Model\Table;

use App\Model\Entity\User;
use Cake\ORM\Query;
use Cake\ORM\RulesChecker;
use Cake\ORM\Table;
use Cake\Validation\Validator;

/**
 * Users Model
 */
class UsersTable extends Table
{

    /**
     * Initialize method
     *
     * @param array $config The configuration for the Table.
     * @return void
     */
    public function initialize(array $config)
    {
        $this->table('users');
        $this->displayField('id');
        $this->primaryKey('id');
        $this->addBehavior('Timestamp');
        $this->hasOne('Roles', [
            'foreignKey' => 'roles_id'
        ]);
    }

    /**
     * Default validation rules.
     *
     * @param \Cake\Validation\Validator $validator Validator instance.
     * @return \Cake\Validation\Validator
     */
    public function validationDefault(Validator $validator)
    {
        $validator
            ->add('id', 'valid', ['rule' => 'numeric'])
            ->allowEmpty('id', 'create')
            ->requirePresence('username', 'create')
            ->notEmpty('username')
            ->requirePresence('password', 'create')
            ->notEmpty('password');

        return $validator;
    }

    /**
     * Returns a rules checker object that will be used for validating
     * application integrity.
     *
     * @param \Cake\ORM\RulesChecker $rules The rules object to be modified.
     * @return \Cake\ORM\RulesChecker
     */
    public function buildRules(RulesChecker $rules)
    {
        $rules->add($rules->isUnique(['username']));
        $rules->add($rules->existsIn(['roles_id'], 'Roles'));
        return $rules;
    }
}