SQL query with 1 fixed and 2 OR conditions

Hi all,
I am trying to find a clean way (without using raw SQL) to do this:
SELECT * FROM table WHERE user_id = 123 AND (role_id IN (1,2,3,4) OR role_id IS NULL)
So I always need to check the user_id, but the role_id may be in the list or NULL.

PHP Code:

$this->usersModel
            ->where('user_id', $userId)
            ->whereIn('role_id', [1,2,3,4])
            ->orWHere('role_id', null)
            ->findAll(); 


But this results in: SELECT * FROM table WHERE user_id = 123 AND role_id IN (1,2,3,4) OR role_id IS NULL.
So it will show also the records where role_id is null, regardless of the user_id.
Any ideas how to do this?