Preheat oven to 375°. Pound chicken breasts with a meat mallet to 1/4-in. thickness., In a food processor, combine spinach, basil, garlic, oil, cheese, walnuts and broth. Cover and process until blended. Stir in tomatoes, artichoke hearts, 1/4 teaspoon salt and 1/8 teaspoon pepper. Spread over chicken. Starting at a short side, roll up and secure with toothpicks. , Place in two greased 11x7-in. baking dishes, seam side down. Sprinkle with remaining salt and pepper. Bake 40-45 minutes or until a thermometer reads 170°. Discard toothpicks before serving.