Pre-heat oven to 450°. Lightly oil a baking sheet with olive oil, and set aside.
Lay the steak or steaks flat and pound the meat until it is about 1/4" to 3/8" thick and of consistent width throughout. The pounding accelerates your cooking time and makes for a tender steak, so don't skimp on this step.
In a medium mixing bowl, blend together the diced onion, chopped tomatoes and Jalapeños, minced garlic, oregano, grated Parmesan cheese and bread crumbs. Spread the stuffing mixture in an even layer over the steak.
Roll the steak up, jelly-roll style, and tie the roll every 2- to 3-inches with butcher's twine.
Warm the olive oil in a heavy skillet over medium-high heat and sear the outside layer of the rolled and stuffed flank steak evenly on all sides. Expect to cook a few minutes and turn regularly to evenly brown the rolled meat.
Place the seared meat roll on the prepared baking sheet and slice 2- to 3-inch wide medallions from the roll, trying to make sure your butcher's twine ends up centered around the medallion. Place the medallions on the baking sheet and bake for about 25 minutes, turning once if desired.
Meanwhile, scrape any residue from the skillet used to sear the steak and deglaze with the white wine. Add hot sauce and reduce the heat. As an option, you can add a bit of cornstarch with a few teaspoons of water if you prefer a thicker sauce. Otherwise, stir the sauce until smooth and strain before serving over the warm steak medallions.