MELT 1 Tbsp. of the butter in large skillet on medium-high heat. Add vegetables; cook and stir until crisp-tender. Add croutons, cheese, water and basil; mix lightly. Remove from heat.
CUT steak horizontally in half to butterfly, being carefuly not to not cut all of the way through the straight side od steak. Open steak; spread bottom half with the vegetable mixture. Roll up, jelly-roll fashion; tie securely with string. Melt remaining 1 Tbsp. butter in same skillet. Add steak; cook until evenly browned on all sides, turning occasionally. Pour tomato sauce over steak; cover. Reduce heat to low.
COOK 1 hour 30 minutes to 2 hours or until steak is cooked through, basting occasionally. Cut into slices; serve topped with the tomato sauce. Sprinkle with additional cheese, if desired.