Broiled Fish Roll-Ups

1 1/2 pounds orange roughy
1/4 cup celery, chopped
1/4 cup mushrooms, chopped
1/4 cup onion, chopped
1/4 cup cooked spinach, chopped
1/2 tsp thyme
1/2 tsp black pepper, freshly ground
lemon juice

Preheat broiler. Rinse fish and pat dry. Combine celery, mushrooms and onions with 1 tsp water in non-stick pan and cook over medium heat until soft and translucent. Remove from heat. Add spinach, thyme and black pepper. Mix well, adding water to moisten if necessary. Divide mixture on fillets. Roll up fish and fasten with toothpicks. Place rolled fillets on broiler. Sprinkle each with lemon juice. Place rack under broiler 4-5 inches from heat. Cook 5-7 minutes, turn carefully and cook 5 minutes more, or until fish flakes easily with a fork.