If you’ve set the image field to return the attachment ID then this should work. You where almost there.
$rows = get_field('hero_images', 'options' ); // get all the rows
$rand_row = $rows[ array_rand( $rows ) ]; // get the first row
$rand_row_image = $rand_row['hero_image']; // get the sub field value
$image = wp_get_attachment_image_src( $rand_row_image, 'full' );
<img src="<?php echo $image; ?>" />
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users