You can also place the butt or roast inside a foil pan, to collect the juices. Just make sure the pan doesn't completely cover the rack. A pan with low sides works best. If you have a BJ's nearby, they sell lasagna pans. They have low sides and are perfect for the Bradley racks. One thing about cooking in a pan is that if you don't have a rack in the pan, the meat will be sitting in it's juices.
Like Edward176, when I'm using foil pans in the Bradley, I tend to monitor the cook more closely.