eZ\Publish\Core\REST\Server\Controller\Role::unassignRoleFromUser PHP Method

    public function unassignRoleFromUser($userId, $roleId)
    {
        $user = $this->userService->loadUser($userId);
        $role = $this->roleService->loadRole($roleId);
        $this->roleService->unassignRoleFromUser($role, $user);
        $roleAssignments = $this->roleService->getRoleAssignmentsForUser($user);
        return new Values\RoleAssignmentList($roleAssignments, $user->id);
    }