In a skillet, melt 1/4 cup of butter; add tomato, celery and parsley. Cook over low heat until vegetables are tender and juices evaporate, about 10 minutes. Remove from the heat; stir in the bread crumbs, blue cheese, egg and salt. Spread over fillets; roll up and secure with toothpicks. Place in a greased 11x1x2-in. baking dish. Melt remaining butter; add lemon juice. Pour over fillets. Cover and bake at 350° for 25-30 minutes or until fish flakes easily with a fork. Remove toothpicks before serving.