Place beef Flank Steak between 2 pieces of plastic wrap. Using smooth side of meat mallet, pound steak to 1/2-inch thickness.
Place tomatoes, 1 tablespoon mustard and capers in food processor; pulse on and off until smooth. Add basil and parsley. Pulse on and off until smooth, scraping sides of food processor container as needed.
Place steak on cutting board so grain is running left to right. Season steak with salt and pepper, as desired. Spread tomato mixture on steak, leaving one inch at top of steak. Starting from bottom, roll steak tightly to form log. Using (8-inch long) pieces of kitchen string, tie log in intervals to yield 8 one-inch slices.
Place beef pinwheels on grid over medium ash-covered coals or over medium heat on pre-heated gas grill. Grill, uncovered, 13 to 15 minutes for medium rare (145° F) to medium (160° F) doneness, turning occasionally, basting with remaining 1 tablespoon mustard, as desired.
Remove string from pinwheels. Place arugula on serving platter. Sprinkle with roasted corn and bell pepper; top with pinwheels. Drizzle balsamic over pinwheels and arugula.
Nutrition information per serving: 289 Calories; 98.1 kcal Calories from fat; 10.9 g Total Fat; 3.5 g Saturated Fat; 0.2 g Trans Fat; 0.8 g Polyunsaturated Fat; 4.7 g Monounsaturated Fat; 73 mg Cholesterol; 444 mg Sodium; 17 g Total Carbohydrate; 3.2 g Dietary Fiber; 28 g Protein; 3 mg Iron; 738 mg Potassium; 7.7 mg NE Niacin; 0.6 mg Vitamin B6; 1.5 mcg Vitamin B12; 4.9 mg Zinc; 27.7 mcg Selenium; 102.4 mg Choline;