Yes, your rooster sounds like he has Mycoplasma gallisepticum.
Edited by Zanily - 10/6/12 at 11:00am
MG is extremely contagious, you should remove the rooster and any other infected birds from the rest of the flock. Once the infected birds have been isolated, thoroughly disinfect the coop and pen to avoid any more birds becoming sick.
When you handle your sick rooster make sure you wash your hands before you go near your other birds. MG can be carried in on shoes, clothing, feeders and drinkers too.
The sooner you treat MG the higher the chance of survival. Some chickens are carriers of MG and have no symptoms, other times MG can be caused by stress. Either way, once your birds have MG it will remain in the flock so bringing any new birds into an established flock of MG carriers is'nt a good idea.
Where have you had the antibiotics from? What does it say on the bottle?