Preheat your oven to 350°F (175°C) and prepare your baking dish by lightly greasing it.

Heat 1 tablespoon of olive oil in a skillet over medium heat. Sauté sliced green bell pepper, onion, and mushrooms for about 5 minutes.

Stir in the thinly sliced roast beef, garlic powder, salt, and pepper into the skillet and cook for an additional 3–5 minutes.

On a flat surface, lay out slices of provolone cheese and distribute a spoonful of the beef and vegetable mixture in the center of each cheese slice.

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

Bake in the preheated oven for 10 minutes until the cheese is golden and gooey.

Allow the roll ups to rest for a few minutes before serving warm.