Preheat oven to 350 degrees. In a large skillet, add oil, chopped onion, and pepper, and saute for 5-6 minutes.
Stir in the cooked corn and beans and cook for another 2-3 minutes.
Melt butter in a sauce pan. Add flour, chili powder, and cumin. Cook until bubbly.
Add tomato sauce and water. Bring to a boil.
Dip corn tortillas in sauce, then put in pan and fill with veggie mixture and cheese and roll up. Pour sauce on top and then more cheese. Bake for 20 minutes, until bubbly. Serve!