How do I get this to work

Hi,

i have code that works, perfectly in the functions.php, I would like to setup these custom fields via the Metabox backend (graphical backend), Problem I am having is , how do i set and run the function cmb_fields_by_user_role when the box is called in the gfx backend ?

	$meta_boxes[] = [
        'title'        => __('Custom Metabox'),
        'id'           => 'custom-metabox',
        'post_types'   => ['cpt'], // CPT
        'fields'       => cmb_fields_by_user_role([
            [
                'type' => 'text',
                'id'   => 'field_1',
                'name' => '<h3>Field 1</h3>',
		'cmb_role'   => array(administrator')
            ],
            [
                'type' => 'text',
                'id'   => 'field_2',
                'name' => '<h3>Field 2</h3>',
		'cmb_role'   => array('author','administrator')
            ],
            [
                'type' => 'text',
				'id'   => 'field_3',
                'name' => '<h3>Field 3</h3>',
		'cmb_role'   => array('administrator')
            ]