private void readObject(java.io.ObjectInputStream in) throws IOException, ClassNotFoundException {
    in.defaultReadObject();
    // transform string names which are serializable back into roles...
    Set roleNames = (Set) in.readObject();
    Set roles = new HashSet(roleNames.size());
    for (final Object roleName : roleNames) {
      String name = (String) roleName;
      roles.add(InternalRole.getRole(name));
    }
    failedRoles = roles;
  }
Returns the required roles that caused this exception. One or more roles failed to receive a
cache distribution message or acknowledge receipt of that message.

@return the required roles that caused this exception
geode-core/src/main/java/org/apache/geode/cache/RegionDistributionException.java