Mangento 2, adding a new image role

image-role.php

<?php
// the group name has to be 'Image Management' rather than 'Image' as it has to match the 'attribute_group_code' rather than the 'attribute_group_name' in the 'eav_attribute_group' table.
// See convertToAttributeGroupCode() in \Magento\Eav\Setup\EavSetup
$this->eavSetup->addAttribute(
    \Magento\Catalog\Model\Product::ENTITY,
    'test_image_role',
    [
        'group' => 'Image Management',
        'type' => 'varchar',
        'frontend' => 'Magento\Catalog\Model\Product\Attribute\Frontend\Image',
        'label' => 'Test image role',
        'input' => 'media_image',
        'class' => '',
        'source' => '',
        'global' => 0,
        'visible' => true,
        'required' => false,
        'user_defined' => false,
        'default' => null,
        'searchable' => false,
        'filterable' => false,
        'comparable' => false,
        'visible_on_front' => false,
        'unique' => false,
    ]
);