Melt butter over medium high heat. Add bell pepper, celery, onions and garlic and cook about 5-7 minutes.
Reduce heat to low and stir in flour and salt, stirring to keep it smooth. Cook, stirring constantly until flour is lightly browned. This should take approximately 20 minutes but can vary.
Add shrimp, stock, lemon juice and seasoning. Cook, stirring until shrimp are done - about 5-8 minutes
Stir in green onion and parsley, reserving a little if desired for garnish.
Serve over rice.