user_table (user_id integer, name varcahr)
user_role_table (user_id integer, role varchar)

Mapping to:

@Entity
class User {
  
  public enum SecurityRole {
    ADMIN, USER, NONE
  }

  ...
  private List<SecurityRole> roles;

}

Essentially @OneToMany only supports entities.

The ENH is to additionally add support for enum, scalar types and embedded beans for @OneToMany.