Mix butter, parsley and garlic together in a bowl and set aside. In a sauce pan over medium heat, melt butter, then add in flour and stir until combined and lightly browned. Add milk and bring to a boil, stirring often. Turn off the heat and let sauce sit 3-4 minutes to cool slightly. Whisk in shredded cheese until melted and smooth. Set aside. Preheat oven to 400*F. Spread garlic butter evenly across the inside of each French roll. Bake rolls for 3-5 minutes. In a large skillet over medium high heat, heat oil, and then add mushrooms and peppers. Sauté for 2-3 minutes. Add in onion and continue sautéing another 2 minutes. Season with salt and pepper. Push vegetables to the side of the pan and add shaved ribeye, season with salt and pepper and let cook 1-1.5 minutes. Assemble beef, vegetables and cheese sauce on the French rolls and serve.