Line a baking pan with parchment paper. Preheat the oven to 375 degrees. For the meantime, heat a pan with 2 tablespoons olive oil. Add the onion, stir, cook until tender or translucent. Add the garlic, stir, add carrots, bell pepper, celery, and mushrooms, stir to mix well. Add cumin, salt, and pepper, stir, taste and adjust the seasonings. Simmer until the veggies are tender. Remove from the heat and set aside.