Second the lemon, as the action of the acidic juices will keep the inner cavity moist. For a crispy skin, rub butter between the skin and the flesh of the bird before roasting. Use fingers to ease the skin off the flesh - comes away quite easily...You can also rub pesto or dry seasoning - paprika, herbs, etc - under the skin, but if the bird is a good quality one and not a '50p special', let the flavour of the chicken come through before using other seasoning.
And suggest you use a rack in the pan - don't just sit the bird on the pan base, but lift it to let air circulate....and start the roasting breast down for 40 mins - this will get a lot of the juices into the flesh, rather the pan...
Make sure the bird is cooked thoroughly too - check the juices run clear when pricked at hte meatiest point - do not rely on time only....
Let the bird rest for a minimum of at least 10 mins before carving - use this time to make up any gravy and sides top go with the meal...