Preheat oven to 450 degrees F (230 degrees C). Grease a 10x15-inch glass baking dish.
Spread potatoes into the baking dish; drizzle olive oil on top. Sprinkle Parmesan cheese and 1 garlic clove over potatoes.
Roast in the preheated oven for 25 minutes.
Melt butter in a large skillet over low heat; season with 1 garlic clove, salt, pepper, and garlic-herb seasoning. Add mushrooms, tomatoes, bell pepper, and onion. Cook and stir until softened, about 5 minutes.
Remove baking dish from the oven. Flip potatoes and stir in mushroom mixture.
Return baking dish to the oven; continue roasting until potatoes are slightly browned, about 15 minutes more.