My condolences......
I hope it goes well with the neighbor. Try not to be confrontational. You are upset and have every right to be, but a dog is a dog.
Does the dog run astray or do they try to keep him/her confined? The only recourse you have is replacement cost. I know the rooster means more to you than that, but in the eyes of the law they are livestock.
The more cordial you are, the more likely they will try to rectify the problem, unless they are just mean people.
You do have the right to defend your livestock if the dog comes onto your property again.
Good luck!