Yes, your roommate can make the "objection for cassation" within 14 days at the administrative court (Verwaltungsgericht).
He should find the adress of the responsable court written at the end of the response letter he received.
The link for the form you sent is correct. In your roommate's case it would be Formularmuster 2 on page 3.
I would not recommend sending the objection by post without consulting a lawyer, even if this is possible.
The case is too important to risk any mistakes.
For further info on possibilities how to proceed please see the following link (in German and Arabic).
Please feel free to ask if you need any further info.