Preheat oven to 350° F.
Melt butter in a saucepan over medium heat. Add onion, celery and mushrooms and sauté for 10 minutes or until tender; let cool.
Combine bread crumbs, salt and pepper in a bowl. Stir in the vegetable mixture; toss gently.
Slice roast three-quarters of the way through to form a pocket. Spoon stuffing into the pocket and secure with toothpicks. Place in a roasting pan. Arrange strips of bacon diagonally on top.
Roast 1 hour, or until cooked to your preference. Serve hot.Servings: 8