Place steak between 2 pieces of plastic wrap. Using smooth side of meat mallet, pound steak to 1/2-inch thickness. Place steak in large food-safe plastic bag or large baking dish. Combine marinade ingredients in small bowl. Pour marinade over steak; turn to coat. Close bag securely or cover dish and marinate in refrigerator 4 hours or as long as overnight, turning occasionally.
Preheat oven to 425°F. Line shallow baking pan with parchment paper. Remove steak from marinade. Reserve remaining marinade; cover and refrigerate. Place steak on cutting board so grain is running top to bottom. Spread tapenade on steak. Arrange spinach evenly on tapenade and sprinkle with feta. Starting from side closest to you, roll the steak tightly to form a log. Using 6 (8-inch long) pieces of kitchen string, tie log in even intervals.
Cut log between string into 6 equal pieces, leaving string in place. Place pieces, cut-side up, on baking pan. In a medium bowl, combine reserved marinade and tomatoes, toss to coat. Arrange tomato mixture around pinwheels. Roast in 425°F for 25 to 35 minutes until instant read temperature inserted horizontally into center registers 165°F. Let stand 5 minutes before serving.