I make a paste/slurry of olive oil, kosher salt, rosemary, lemon zest & lemon juice and rub it inside & outside of the chicken. You can also add a couple of cloves of garlic if you wish, minced or put through a press. Put the juiced/zested lemon haves into the cavity. Loosen the skin on the breast and slide in about 1-2 T butter each side. Start the roast at 400º for 20 minutes, then lower to 350º until a thermometer inserted into the thickest part of the thigh tells you the bird is done. You can substitute orange zest/juice for the lemon and herbes de provence for the rosemary.

this is my favorite: http://www.food52.com/recipes/2572_best_roast_chicken

Last week I tried Thomas Keller's simple method. Extremely simple and the best roast chicken I've made. The combination of the high heat and the generous sprinkle of kosher salt and ground pepper elevated the dish. The skin is divinely crisp and the meat moist. I also placed it in a cast iron skillet.
http://www.epicurious.com/recipes/food/views/My-Favorite-Simple-Roast-Chicken-231348

This is how I do it: Preheat a cast iron skillet in the oven at 450. Make a compound butter mixture with rosemary, thyme, parsley, garlic, salt, and pepper; stuff it under the skin and rub it on the outside. Place the chicken in the hot skillet, then put it back in the oven and roast it for about 35 minutes (for a 3-4 lb chicken) or until the internal temp is 165. Comes out perfect and juicy every time.