Evenly divide roast on the bottoms of hoagie rolls. Place on a baking sheet and pop in the oven to heat up.
In a medium sauté pan, heat olive oil over a medium heat, add onions and green peppers. Saute until softened, about 5-7 minutes. Season with salt and pepper. Set aside.
In a small saucepan stir together grated cheese and evaporated milk. Turn the heat on a medium-low, and stir until cheese is completely melted. Season with salt and pepper. Note: Serve right away.
Once roast beef is warm, top with sautéed onions and green pepper. Drizzle with cheese sauce.
Recipe by Cooking for Keeps at https://www.cookingforkeeps.com/skinny-roast-beef-pepper-cheddar-sandwiches/