Thanks John worked it out from your input.
Here’s the code if anyone else needs help as I looked around for quite a while before raising a ticket.
add_action (‘acf/save_post’, ‘add_role_on_selection’);
function add_role_on_selection ($post_id) {
// Get newly saved values.
$values = get_fields( $post_id );
// Check the new value of a specific field.
$selected = get_field(‘stall_catergory’, $post_id);
$user = wp_get_current_user();
if( $selected == ‘general’) {
$user->add_role(‘general’);
}
if( $selected == ‘food’) {
$user->add_role(‘food’);
}
if( $selected == ‘hot food’) {
$user->add_role(‘hot_food’);
}
}