Preheat oven to 350 degrees. Poke holes with a fork in one pie crust. Put both crusts in refrigerator until ready to fill.
In a skillet, melt butter, add flour and whisk into a paste. Cook roux for 5 minutes. Add onion, bell pepper, and celery. Cook until vegetables are tender. Add crawfish, green onions, parsley and seasoning. Cook for 2 more minutes. Add filling to pie crust with the holes. Flip the other crust over the top. Crimp edges with a fork, cut air holes in the top, and cut off the excess dough around the edges.