Deep Dish Meat Pie

1 lb ground beef
1/4 C chopped onion
1 (10oz) pkg frozen peas & carrots, cooked and drained
1 C chopped cooked potatoes
1/2 lb (8oz) Velveeta, cubed
2 Tbsp butter or margarine
2 Tbsp flour
1/2 tsp salt
1 C cold water
1 (8oz) pkg crescent rolls

Brown meat; drain. Add onion; cook until tender. Add vegetables and cheese, mix well. Spoon into 12x8" baking dish. Melt butter in saucepan. Stir in flour and salt, cook 2 minutes. Gradually stir in water until smooth. Cook on medium heat until mixture boils and thickens. Reduce heat to low; simmer 3-5 minutes. Pour over meat. Separate dough into 4 rectangles; firmly press perforations to seal. Place over meat mixture. Bake at 375 for 20-25 minutes or until golden brown.