Remove baking dish from oven. Pour off juices into a heat proof bowl. Remove bacon from roast and set aside. Flip roast over so it's fat side up. Cover with foil and return to oven for an additional hour.
While the roast is continuing to cook, finish bacon off in a saucepan. Set aside. In the bacon fat in the sauce pan, cook the diced onion over medium heat for about 10-15 minutes, until it has softened. Tear the bacon into 1/2 inch pieces Add the juices from the baking pan, barbecue sauce, and bacon to the saucepan. Simmer for 15 minutes, or until the sauce has reduced and thickened.