In a large cast-iron or other heavy skillet, saute red pepper and mushrooms in oil until tender. Add garlic; cook 1 minute. Add the rice, beans, corn, green onions, cumin, pepper and salt. Cook and stir until heated through, 4-6 minutes.
Spoon 3/4 cup onto each tortilla. Sprinkle with cheese; drizzle with salsa. Fold sides of tortilla over filling; serve immediately.