You can hook into the acf/pre_save_post filter and then change the user roles using the WP_User class. A user’s role can be set by creating an instance of the WP_user class, and calling the add_role() or remove_role() methods.
The code would look like so:
$u = new WP_User( $user_id );
// Remove role
$u->remove_role( 'subscriber' );
// Add role
$u->add_role( 'editor' );
Welcome to the Advanced Custom Fields community forum.
Browse through ideas, snippets of code, questions and answers between fellow ACF users