Trussing it wrong or roasting at the wrong temperature and length of time can cause your chicken to be dry or over cooked. In addition to trussing and roasting, seasoning is pertinent for achieving a flavorful bird, and generously. You have to account for the salt and pepper you put on the outside, as well as the inside cavity, to flavor the entire thing so you have to add enough for it to be seasoned throughout. I know it may seem like you are putting a lot on as you're prepping the chicken, but chances are it could use a little more.