Hi
I'm sorry you lost your Buff Orp and now the rooster is displaying symptoms. Yes it is contagious but it takes a minimum of 3 weeks from infection to the first symptoms appearing..... it can be significantly longer. Outbreak of symptoms is usually triggered by stress. That can be integration into a new flock or surge of hormones during adolescence or change of hormones at moult or a bad storm or a predator attack. Because the disease has dormant phases, it is very difficult to know which birds have been infected and which have not, but you have to assume all your birds have been exposed. The disease is caused by a Herpes virus similar in some respects to cold sores in humans. You cannot tell who carries the virus and who doesn't until they have a cold sore break out and they actively shed the virus whilst they are having an outbreak. I have had quite a few birds recover from an outbreak but they will always be at risk of further outbreaks because they will always have the virus. I had one very special pullet recover from two outbreaks of the disease. The first time she was fine one day, lame the next and floundering on her side in the classic Marek's splits position unable to get up. 2 days later you would not know there had ever been anything wrong. A month or so later she had her second attack and it took several months of supportive care some of which she was nest bound for but she eventually regained enough mobility to return to free ranging with the flock and had a good quality of life until she very sadly fell victim to a fox
It depends on the severity of the strain of Marek's you have. I am fortunate to have a milder one but
@Nambroth who wrote the article linked by Excessive above, has a more aggressive strain. You will only figure out how hot your strain is (if in fact you do have Marek's, although it seems pretty likely) by the number of birds it kills. I find the most beneficial things are a good quality poultry vitamin supplement like Nutri Drench or Poultry Cell to support the immune system and probiotics or fermented feed to support the gut. Keeping them as happy and stress free is also extremely important..... ensuring plenty of space if they are penned and lots of things to do to keep them occupied.
Once they lose interest in food, that is when I euthanize but as long as they are bright eyed and eating and prepared to fight it, I give supportive care. Others cull at the first sign of symptoms to prevent an increase in the reservoir of infected material in the flock's environment.... which is probably very wise .... but I can't do it to a bird that in my experience might recover from an outbreak. Once they stop eating, they decline pretty rapidly, so that is my cut off point.
If you have any other questions, feel free to ask.
Hens go broody when you don’t want them to… and won’t go broody when you do. 
