Bring broth to a boil in large saucepan. Add onions, reduce heat and simmer 3 minutes. Add turkey, return to boil. Reduce heat, cover and simmer 9-10 minutes or until turkey is no longer pink. Remove turkey with a slotted spoon and place in a 13x9" baking dish, sprayed with non stick cooking spray.
Increase heat and return broth to boil. Add potatoes, rosemary, salt, pepper. Simmer 2 minutes. Return to boil and stir in both bags of mixed vegetables. Simmer covered for 10 minutes. Remove vegetables & potatoes with a slotted spoon to a colander (strainer) set over a boil to catch any broth. Place vegetables in baking dish with turkey.
Preheat oven to 375^. Blend milk with cornstarch in a small bowl until smooth. Add enough milk to broth to equal about 3 cups. Heat in a saucepan over med-High heat; mix in cornstarch milk mixture, stirring constantly until mixture comes to a boil, boil for 1 min. Remove from heat, pour over turkey and vegetables.
Roll out crescents on a piece of wax paper, separate at perforations,arrange dough pieces decoratively over turkey & vegetables. Bake 13-15 minutes until golden brown.