Grease a 9×13-inch baking dish with nonstick spray and set aside. Heat 2 tablespoons olive oil in a Dutch oven over medium-high heat. Once hot, whisk in 2 Tablespoons all-purpose flour, 2 teaspoons chili powder, 1 teaspoon ground cumin, ½ teaspoon salt, ¼ teaspoon ground black pepper, and ¼ teaspoon dried oregano. Cook for 5 minutes, whisking often.
Add the diced 1 pound boneless skinless chicken breast and saute this for 5 to 10 minutes or until the chicken is cooked through. Then stir in the 4 ounces green chilies and cook just until heated through. Spoon just enough enchilada sauce to coat the bottom of the prepared baking dish.
Spread a little enchilada sauce on each tortilla and place about ¼ cup of filling down the center of each tortilla. Roll up the tortillas and place them seam-side down next to one another in the baking dish. Spread the remaining enchilada sauce over top. Sprinkle the 2 cups Mexican blend cheese evenly over the top. Bake for 15 minutes or until the cheese is bubbly. Serve hot with your favorite toppings.