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You might want to post about your roo in the Emergencies forum. https://www.backyardchickens.com/f/10/emergencies-diseases-injuries-and-cures Hopefully somebody over there will be able to advise you but, they seem to be prone to vitamin deficiencies and wry neck or star gazing is a problem with them, sometimes its a deficiency of Vit B1 or Thiamine, which plus Vit E and Selenium they recommend giving them.
Did this come on suddenly? Silkies are very prone to head injuries . Sometimes they just have the twisted neck, others will walk backwards, do somersaults, move around with their head, between their legs, just about touching the floor.
Massaging the neck gently a few times a day, in the direction it should be - can be helpful. Some silkies benefit from getting Polyvisol infant drops, 2 or 3 times a day, a few drops of vitamin E (squeezed from a capsule). They will usually eat this if you put it on a sliced grape. In some cases prednosone prescribed ONLY by a vet,or administered under his instructions can bring faster relief. This is a condition that can be lengthy to deal with- the plus side is I've never heard of a silkie dying from it UNLESS their caretaker doesn't want to bother with them and puts them down.
Do you know if he bumped his head or was pecked by another bird? Other breeds can have wry necks also but, in silkies it is thought of as "silkie syndrome" because it is common in the breed, especially the silkies with high vaulted skulls - where the bones didn't fill in completely - they just have a layer of skin closing their skull.