On a hard, flat surface, with the bottom of a glass (or with a mortar and pestle), coarsely crush peppercorns. Put in a small bowl and mix with parmesan cheese and dried tomatoes.
Rinse flank steak and pat it dry; trim off and discard fat. Lay steak flat on a board and spread peppercorn mixture evenly over meat. Starting from one end, roll steak tightly around filling into a neat, compact log. Tie with heavy cotton string at 2-inch intervals. Wrap log tightly in plastic wrap and chill up to 1 day.
Place a 10- to 12-inch frying pan with ovenproof handle over high heat. When hot, remove rolled steak from plastic wrap, add steak to pan, and turn to brown evenly on all sides, 3 to 4 minutes total. Transfer pan with steak to a 400° regular or convection oven; bake until a thermometer inserted in center of thickest part of meat registers 135° for medium-rare, 45 to 50 minutes (35 to 40 minutes in convection), or until beef is as done as you like.
Transfer steak to a rimmed cutting board and let rest about 5 minutes. Remove and discard strings. To serve, cut steak crosswise into 1/4- to 1/2-inch-thick slices.