Acting on roles being revoked/granted

As I said in the other issue I am working on hard coding user inheritance for my use case since I have to move forward but I've run into a bit of a snag when trying to grab the roles as they are revoked/granted.

My initial thought was to act on a user being added to a group so I figured I would use hook_entity_insert on group_membership entities but the membership didn't contain roles at that point like I expected it to. I'm only using gadd to allow members into groups so the offending code snippet appears to be

function gadd_add_member_form_submit($form, &$form_state) {
  global $user;

  $values = array(
    'gid' => $form_state['build_info']['args'][0]->gid,
    'uid' => $form_state['values']['uid'],
    'added_on' => REQUEST_TIME,
    'added_by' => $user->uid,
  );

  // Create and save the membership.
  $group_membership = entity_create('group_membership', $values);
  $group_membership->save();

  // Grant the predetermined roles.
  $group_membership->grantRoles(array_filter($form_state['values']['roles']));

  // Show a confirmation message.
  drupal_set_message(t('Added %user', array('%user' => $form_state['values']['user'])));
}

When I added roles to the values array it broke things. Looking into the code I can't tell why it breaks things so that plan is out the window. Though in my searches I did stumble upon the addMember() function which I think should be called to add the member instead of the code being used.

Since that wasn't working I figured well I can just propagate the new membership with no roles all the way down using entity_insert and since roles aren't added on creation of a membership they must trigger a hook_entity_update where I can generically act on all roles being granted/revoked. The problem I ran into here is that granting or revoking roles doesn't trigger a hook_entity_update like I expected it would. Which leaves me stuck.

Any suggestions on how to work around this? I'm still picking up drupal and php so perhaps I am missing another way that this could be accomplished but this seemed to me like the way to go about it.