For sweet pepper sauce, in a blender container or food processor bowl combine roasted peppers, half-and-half or light cream, and vinegar. Cover; blend or process until smooth. Pour into a small bowl. Cover; set aside.
In another small bowl stir together cream cheese, parsley, garlic, and black pepper; set aside. In a large skillet cook mushrooms and onion in hot margarine or butter over medium-high heat for 4 to 5 minutes or until mushrooms are tender and most of the liquid evaporates. Remove from heat; stir in prosciutto or ham.
Place one crepe in the bottom of a lightly greased 9-inch pie plate. Spread about one-fifth of the cream cheese mixture over crepe; sprinkle with about one-fifth of the mushroom mixture. Add a second crepe (if using square crepes, set second crepe at a slight angle to the first crepe so points are staggered). Add another one-fifth of the cream cheese and mushroom mixtures as before. Repeat with the remaining crepes, cream cheese mixture, and mushroom mixture, ending with mushroom mixture. Cover loosely with foil.
Bake in a 350 degree F oven about 20 minutes or until heated through. Cut into wedges to serve. Pass sweet pepper sauce. Makes 6 to 8 servings.