Preheat oven to 425°F. Place Italian dressing, tomatoes and water in blender or food processor container. Cover; process until smooth. Divide mixture evenly into thirds; reserve 2/3 tomato mixture.
Combine potatoes and peppers and 1/3 tomato mixture in large bowl; toss to coat. Place on rimmed baking sheet lined with parchment. Set aside.
Spread 1/3 tomato mixture evenly onto all surfaces of beef roast. Place roast on vegetables. Do not add water or cover. Roast in 425°F oven 30 to 40 minutes for medium rare; 40 – 50 minutes for medium doneness.
Remove roast when instant-read thermometer registers 135° for medium rare; 150° for medium. Transfer roast to carving board; tent loosely with aluminum foil. Let stand 20 – 25 minutes. (Temperature will continue to rise about 10°F to reach 145°F for medium rare; 160°F for medium) Meanwhile, increase oven temperature to 475°F. Stir vegetables and return to oven for 15 – 20 minutes or until desired doneness.
Carve roast across the grain into slices. Serve with vegetables. Coat all with remaining sauce. Sprinkle with parmesan. Sprinkle with parsley, if desired.
Nutrition information per serving: 265 Calories; 81.9 kcal Calories from fat; 9.1 g Total Fat; 3.1 g Saturated Fat; 0.01 g Trans Fat; 0.8 g Polyunsaturated Fat; 4.2 g Monounsaturated Fat; 67.4 mg Cholesterol; 551 mg Sodium; 21.4 g Total Carbohydrate; 3.4 g Dietary Fiber; 25 g Protein; 2.2 mg Iron; 708.2 mg Potassium; 10.5 mg Niacin; 0.8 mg Vitamin B6; 1.3 mcg Vitamin B12; 4.6 mg Zinc; 27.6 mcg Selenium; 99.46 mg Choline;