When I roast a chicken I like to stuff the body cavity with herbs, citrus and other aromatic ingredients, and trussing the chicken helps to hold those items in place. Here you see a trussed chicken ready to roast.
At the bottom of the roasting pan I've placed a few slices of bread, which will soak up the drippings as the chicken roasts while also turning nice and brown and toasty — delicious! Here's a simple roasted chicken recipe.