Hi 
@Clm300 Welcome To BYC
Can you post some photos of your rooster?
What does his poop look like?
What do you feed?
Any respiratory symptoms?
The craning of the neck could be an indication of a crop problem as suggested by 
@micstrachan  so it's a good idea to make sure it's emptying properly overnight.
The holding/tilting of the head to the side could also be Wry Neck which is a neurological symptom-some causes include vitamin/mineral deficiency, head injury/trauma and diseases like Marek's and Avian Lymphoid Leukosis.
I would offer him poultry vitamins that contain E and B vitamins.  See if he will eat a little egg or tuna for you, that will provide some Selenium.   Try to keep him hydrated.
Since you started the Tylan50  I would finish the course, but you may want to check your dosage.  How much does your rooster weigh?  Tylan50 is most effective when given 2-3times a day as well.
Let us know how he's doing.