Bacon drippings or melted butter to roast a chicken

Butter or neither, just use a good quality chicken. Bacon tends to dominate - I think it could mask the chicken's more understated flavor and hijack the dish. Maybe roast your root vegetables separately with a little bacon fat, if you want that flavor in the meal too.

Neither would also be fine. There are plenty of great roast chickens with nice crispy skins that haven't had any additional oils brushed over them.

I suppose if you want your chicken to taste somewhat of bacon...use the drippings. I'm a purist when it comes to chicken so I generally stick to butter or olive oil. I don't think you can generally go wrong with fat, though.

Both? :-) I don't usually brush the chicken before I roast it. I like to tuck some butter or extra flavoring under the skin and inside the cavity to season the meat because the flavoring on the outside will not penetrate the meat inside.