Select saute or browning setting on a 6-qt. electric pressure cooker. Adjust for medium heat; add 1 teaspoon oil. When oil is hot, brown one roast half on all sides. Remove; repeat with remaining beef and oil. Add coffee to pressure cooker. Cook 1 minute, stirring to loosen browned bits from pan. Press cancel. Add mushrooms, green onions, garlic, liquid smoke if desired, salt, chili powder, pepper and beef.
Lock lid; close pressure-release valve. Adjust to pressure-cook on high for 50 minutes. Let pressure release naturally. A thermometer inserted in beef should read at least 145°. Press cancel.
Remove roast and vegetables to a serving platter; tent with foil. Let stand 10 minutes before slicing. Reserve 2 cups cooking juices; discard remaining juices. Transfer back to pressure cooker. In a small bowl, mix cornstarch and water until smooth; stir into pressure cooker. Select saute setting and adjust for low heat. Simmer, stirring constantly, until thickened, 1-2 minutes. Serve with roast and vegetables. Freeze option: Place sliced pot roast and vegetables in freezer containers; top with sauce. Cool and freeze. To use, partially thaw in refrigerator overnight. Heat through in a covered saucepan, stirring gently and adding a little water if necessary.