It sounds like he had a respatory illness going on, thats why I asked if you had any type of antibiotics on hand.
I suggest every one has some for these types of unexpected illnesses, Because it never fails when you need something the most the stores are closed, its at night, or the weekend.
Im so very sorry about your roo. He looked like he was a great chicken. I am sure you took very good care of him. I to just had three silkie hens pass away the other month. So I know what you are going through. Just think now he is now heathy and happy.