Symfony many role for user

I have problem, early my entity have one role and this is sufficiently for project. But now my entity need have many role like ROLE_DEVELOPER, ROLE_COMPANY and when user doing some operation for entity add new role. And how best away for this situation, create new entity or change field role in array or what ?

class User implements UserInterface
{
/**
 * @var integer
 *
 * @ORM\Column(name="id", type="integer")
 * @ORM\Id
 * @Expose()
 * @ORM\GeneratedValue(strategy="AUTO")
 */
  protected $id;

/**
 * @Gedmo\Slug(fields={"firstName", "lastName"}, separator="-", updatable=true)
 * @ORM\Column(name="name", type="string", options={"default": "Company"}, length=255, nullable=false)
 * @Assert\Length(min=3, max=255)
 */
protected $username;

/**
 * @var string
 *
 * @ORM\Column(name="password", type="string", length=80, nullable=true)
 */
protected $password;

/**
 * @ORM\ManyToMany(targetEntity="Role")
 * @ORM\JoinTable(name="security_users_roles")
 */
protected $roles;

public function __construct()
{
    parent::__construct();
    $this->roles = new ArrayCollection();
}

//... existing setters/getters

/**
 * Returns an ARRAY of Role objects with the default Role object appended.
 * @return array
 */
public function getRoles()
{
    return array_merge( $this->roles->toArray(), array( new Role( parent::ROLE_DEFAULT ) ) );
}

/**
 * Returns the true ArrayCollection of Roles.
 * @return Doctrine\Common\Collections\ArrayCollection 
 */
public function getRolesCollection()
{
    return $this->roles;
}

/**
 * Pass a string, get the desired Role object or null.
 * @param string $role
 * @return Role|null
 */
public function getRole( $role )
{
    foreach ( $this->getRoles() as $roleItem )
    {
        if ( $role == $roleItem->getRole() )
        {
            return $roleItem;
        }
    }
    return null;
}

/**
 * Pass a string, checks if we have that Role. Same functionality as getRole() except returns a real boolean.
 * @param string $role
 * @return boolean
 */
public function hasRole( $role )
{
    if ( $this->getRole( $role ) )
    {
        return true;
    }
    return false;
}
/**
 * Adds a Role OBJECT to the ArrayCollection. Can't type hint due to interface so throws Exception.
 * @throws Exception
 * @param Role $role 
 */
public function addRole( $role )
{
    if ( !$role instanceof Role )
    {
        throw new \Exception( "addRole takes a Role object as the parameter" );
    }

    if ( !$this->hasRole( $role->getRole() ) )
    {
        $this->roles->add( $role );
    }
}

/**
 * Pass a string, remove the Role object from collection.
 * @param string $role 
 */
public function removeRole( $role )
{
    $roleElement = $this->getRole( $role );
    if ( $roleElement )
    {
        $this->roles->removeElement( $roleElement );
    }
}

/**
 * Pass an ARRAY of Role objects and will clear the collection and re-set it with new Roles.
 * Type hinted array due to interface.
 * @param array $roles Of Role objects.
 */
public function setRoles( array $roles )
{
    $this->roles->clear();
    foreach ( $roles as $role )
    {
        $this->addRole( $role );
    }
}

/**
 * Directly set the ArrayCollection of Roles. Type hinted as Collection which is the parent of (Array|Persistent)Collection.
 * @param Doctrine\Common\Collections\Collection $role 
 */
public function setRolesCollection( Collection $collection )
{
    $this->roles = $collection;
}
}

entity Role

class Role implements RoleInterface
{
/**
 * @ORM\Id
 * @ORM\Column(type="integer", name="id")
 * @ORM\GeneratedValue(strategy="AUTO")
 */
private $id;
/**
 * @ORM\Column(type="string", name="role", unique="true", length="70")
 */
private $role;
/**
 * Populate the role field
 * @param string $role ROLE_FOO etc
 */
public function __construct( $role )
{
    $this->role = $role;
}
/**
 * Return the role field.
 * @return string 
 */
public function getRole()
{
    return $this->role;
}
/**
 * Return the role field.
 * @return string 
 */
public function __toString()
{
    return (string) $this->role;
}
}