FOS\UserBundle\Model\UserInterface::removeRole PHP Method

    function removeRole($role);

 /**
  *
  */
 public function updateRoles(UserInterface $user)
 {
     $roles = $user->getRoles();
     $roleRepository = $this->objectManager->getRepository('WeavingTheWebUserBundle:Role');
     foreach ($roles as $role) {
         $roleName = (string) $role;
         $roleEntity = $roleRepository->findOneByRole($roleName);
         $user->removeRole($role);
         $user->addRole($roleEntity);
     }
 }