Preheat the oven to 275 degrees F (135 degrees C).
Pour vegetable oil into a large oven-safe pot over medium-high heat. Season the chuck roast with salt and black pepper. Brown the meat on both sides in the hot oil, and transfer to a plate.
Stir carrots, celery, and onion into the pot, and cook and stir until vegetables start to release their juices, about 3 minutes; loosen any brown flavor bits on the bottom of the pot. Add butter, and cook until the onions are translucent, about 5 minutes. Then sprinkle in rosemary, stir the vegetables, and return the roast to the pot. Cover the pot with a lid.
Roast in the preheated oven until the chuck roast is tender, about 2 1/2 to 3 hours. Season vegetables with additional salt and black pepper, if desired.
