unnecessary loading all roles?

At the moment you get all the user roles for ALL user_loads:

  // Add the group roles to $user->roles if this is a group
  // This should only be effective until the next global $user call
  if ($op == 'load') {
    $roles = og_user_roles_all_roles($user); // This returns normal $user->roles and includes OG roles if any
    $user->roles = $roles;
  } // end $op load

However it is only necessary if you are the current user or want to display the users roles. Because the chance you want to display the users roles is not that big I would normally only want to get the roles if it were the current user.

Maybe make it something like this:

  // Add the group roles to $user->roles if this is a group
  // This should only be effective until the next global $user call
  if ($op == 'load' && ($GLOBALS['user']->uid == $user->uid || variable_get('user_roles_always_get_roles', 0))) {
    $roles = og_user_roles_all_roles($user); // This returns normal $user->roles and includes OG roles if any
    $user->roles = $roles;
  } // end $op load

Another little performance gain

    $query = 'SELECT r.rid, r.name FROM {role} r INNER JOIN {og_users_roles} ogr ON r.rid = ogr.rid INNER JOIN {og_uid} ogu ON ogu.uid = ogr.uid AND ogu.nid = ogr.gid WHERE ogr.uid = %d AND ogr.gid = %d AND ogu.is_active = 1';
    $results = db_query($query, $uid, $gid);
  
    //
    // Create an array of these roles;
    //
  
    while ($row = db_fetch_array($results)) {
      $x1 = $row['rid'];
      $ogroles[$x1] = $row['name'];
    }

Replace with:

  static $querie_results;
  
  if (isset($querie_results[$uid.'_'.$gid])) {
    $ogroles = $querie_results[$uid.'_'.$gid];
  }
  else {
    $query = 'SELECT r.rid, r.name FROM {role} r INNER JOIN {og_users_roles} ogr ON r.rid = ogr.rid INNER JOIN {og_uid} ogu ON ogu.uid = ogr.uid AND ogu.nid = ogr.gid WHERE ogr.uid = %d AND ogr.gid = %d AND ogu.is_active = 1';
    $results = db_query($query, $uid, $gid);
  
    //
    // Create an array of these roles;
    //
  
    while ($row = db_fetch_array($results)) {
      $x1 = $row['rid'];
      $ogroles[$x1] = $row['name'];
    }
    $querie_results[$uid.'_'.$gid] = $ogroles;
  }