Adding a select box to a tableselect

I'm trying to use the technique outlined in this blog post:

https://www.hexblot.com/blog/drupal-tableselect-fields

to add a select box to a tableselect, but there are a couple of issues:

• The default value is not being respected (I've tried using #value and #default_value)
• The roles element is empty on submit

Any idea what I'm missing? Here's my code:

foreach ($query as $row) {
  $member = user_load($row->etid);
  $roles = og_get_user_roles('node', $org->nid, $member->uid, FALSE);
  $role = reset($roles);
  $role = $role ? $role : 'campaigner';
  $rows[$member->uid] = [ 
    'mail' => $member->mail,
    'current_role' => $role,
    'role' => [ 
      'data' => [ 
        '#type' => 'select',
        '#name' => 'role[' . $member->uid . ']',
        '#options' => [ 
          'campaigner' => 'Campaigner',
          'administrator' => 'Administrator',
        ],
        '#default_value' => $role,
      ],
    ],
  ];
} 

$form['team_heading']['team'] = [
  '#type' => 'tableselect',
  '#header' => [
    'mail' => t('Email'),
    'current_role' => t('Current Role'),
    'role' => t('V2 Role')
  ],
  '#options' => $rows,
  '#js_select' => FALSE,
  '#default_value' => drupal_map_assoc(array_keys($rows)),
];

$form['role'] = ['#type' => 'value'];