Heat oven to 325 degrees F. Combine 3 tablespoons Dijon-style mustard, 1 tablespoon thyme and 1/2 teaspoon pepper in small bowl. Spread mustard mixture evenly over all surfaces of beef roast. Press bread crumbs evenly onto roast over mustard.
Place roast on rack in shallow roasting pan. Insert ovenproof meat thermometer so tip is centered in thickest part of beef, not resting in fat. Do not add water or cover. Roast for 1 3/4 to 2 hours for medium rare, 2 1/4 to 2 1/2 hours for medium doneness.
Meanwhile prepare vegetables. Cut shallow X into bottom of each Brussels sprout. Toss Brussels sprouts, carrots, oil, thyme, salt and pepper in large bowl. Transfer to metal baking sheet. Cover tightly with aluminum foil. Roast in 325 degree F oven. Roast 1 to 1-1/4 hours or until crisp-tender. Uncover baking sheet; continue roasting 5 minutes or until lightly browned.
Remove roast when meat thermometer registers 140°F for medium rare; 155°F for medium. Transfer roast to carving board; tent loosely with aluminum foil. Let stand, covered, 20 minutes. (Temperature will continue to rise about 5°F to reach 145°F for medium rare; 160°F for medium.)
Meanwhile prepare Mustard Sauce. Heat oil in small saucepan over medium heat until hot. Add shallots; cook and stir 3 to 5 minutes or until tender. Add Dijon-style mustard, mustard seeds and dry mustard; cook and stir 30 seconds. Remove from heat; stir in lemon juice until well blended. Add sour cream, parsley and pepper; stir until smooth. Keep warm.
Carve roast into thin slices. Serve with vegetables and Mustard Sauce.