Preheat your oven to 350°F (175°C).

In a large skillet, heat 1 tablespoon of olive oil over medium heat. Add the green bell pepper, onion, and mushrooms. Sauté for about 5 minutes until softened.

Add the thinly sliced roast beef to the skillet, along with garlic powder, salt, and pepper. Cook for another 3-5 minutes until heated through.

Lay out the provolone cheese slices and spoon the beef and vegetable mixture onto each slice.

Roll each provolone slice tightly around the filling and place seam-side down in a baking dish.

Bake for 10 minutes or until the provolone cheese is melted and bubbly.

Let the roll ups rest for a few minutes before serving.