Cut carrots, onion, potatoes, and celery into large chunks.
Place the roast in a large crockpot.
Mix cornstarch with tomato sauce, then spread over beef; top with vegetables, parsley, and bay leaf.
Cover and cook on low 6-8 hours or until the internal temperature of the meat reaches 145° F. Allow meat to rest for 3-5 minutes before cutting (or shredding).
Dice tomatoes and cucumber; shred lettuce (if necessary). Add to a large mixing bowl and toss with dressing.
Serve roast and veggies with salad and applesauce on the side.