In a medium saucepan, heat 1 tablespoon oil over medium heat. Add the onion and saute briefly; add the flour and salt; cook, stirring, for about 2 minutes. Add the milk slowly, whisking until well blended and just beginning to thicken. Add fish and heat through. Cut the rolls in half, pull some of the breading out of the center; do not break the crust. Brush the inside with some of the remaining olive oil; fill with fish mixture; replace tops and brush with oil. Place on a baking sheet and bake at 375 degrees F until the rolls are browned.
Per Serving: 346 Calories (24.5% from fat); 9g Fat (2g Sat, 4g Mono, 1g Poly); 23g Protein; 41g Carbohydrate; 2g Dietary Fiber; 43mg Cholesterol; 553mg Sodium. Food Exchanges: 2 1/2 Grain (Starch); 2 Lean Meat; 1 1/2 Fat.