It all comes down if you have enough proof or not. I think you will have to get enough documentation of your parents. You have to have proof that your father has a green card and your mother did not became us citizen at the time of your birth. Perhaps if you have your mother and father's naturalization papers dated later than your birth and maybe your father's green card.
Unfortunately, the HK immigration office has to have enough proof beyond the doubt that your are qualified for ROA.