When someone figures out how to cook a perfect roast chicken let me know. I'll pay big bucks... (well, maybe not "Big", but a decent amount...
Overcooked = Tough.
Breast meat should be 165ºF throughout (including near the breastbone/ribs).
Legs are a different story. Not just 180ºF, but cooked long enough so the collagen melts out and gives the meat a tender/unxiousness (joint wiggle method applies here).
Oh, and the skin needs to be golden brown all the way round'.
I usually break the chicken down and roast pieces separately.
I'm kinda picky though...
I roast on an elevated rack with onions/giblets (minus liver) underneath. Then I make a good Au Jus to serve with the chicken pieces.