Start with the glaze so it can simmer while you cook the steak. In a small bowl, add the cornstarch into the broth until smooth.
Take a small saucepan and add the balsamic vinegar, red wine, brown sugar, garlic, rosemary, black pepper, and salt and bring to a low boil. Stir in the broth mixture and boil for 1 minute, then reduce to low heat and simmer, stirring occasionally.
Prepare the vegetables by cutting the peppers, zucchini, and onion into strips around ¼ inch thick and about the length of the steak.
In a 12-inch skillet, heat 1 tablespoon of olive oil on medium-high heat. Add the peppers, zucchini, onion, mushrooms, and season with salt and pepper to taste. Sauté until crisp, 1½ to 2 minutes. Remove from heat and take the vegetables out of the pan so they don’t keep cooking.
Prepare the steak by lightly brushing both side with olive oil (use around 1 tablespoon) then sprinkle with salt, pepper, and chopped rosemary.
Divided the vegetables between the pieces of steak, placing them at the end across a short side. Lay them perpendicular to the length of the steak – they should be wider, so they stick out at the ends.
Start with the side of the steak with the vegetables, carefully roll up the steak and use a toothpick to secure.
Put the skillet back on the heat and add 1 tablespoon of olive oil on medium-high heat. Place the steak rolls in the pan, seam side down, and cook for 1 minute per side or until the desired doneness.
Remove the rolls to a platter, removing the toothpicks. Remove the rosemary sprigs and garlic cloves from the glaze and serve over the steaks.