Stuff roast with garlic, salt, pepper and Cajun seasoning. In a large pot of boiling water, boil roast until meat is slightly pink. Remove from water.
Lay roast in a 9×13 inch baking dish lined with aluminum foil. Cover in ketchup and mustard. Then cover with more foil and bake in the preheated oven for 1 1/2 to 2 hours or until internal temperature has reached 145 degrees F (63 degrees C).