Combine 1/2 cup melted butter, onion, garlic, parsley, salt, and pepper; mix well. Spoon one-half of mixture onto roast, spreading to within 2 inches of edge. Roll up jellyroll fashion, enclosing the stuffing completely. Tie roast securely with string. Cover outside of roast with remaining onion mixture.
Place roast in a well-greased shallow roasting pan. Insert meat thermometer, if desired. Pour 2 tablespoons melted butter over roast. Bake, uncovered, at 450° for 15 minutes. Add wine. Reduce heat to 325°, and bake an additional 1 1/2 hours or until meat thermometer registers 170° (well done), basting occasionally. Transfer roast to a serving platter; remove string. Let stand 10 minutes before slicing. Reserve pan drippings.
Remove excess grease from pan drippings, and discard. Strain pan drippings into a medium saucepan. Bring mixture to a boil; reduce heat, and cook over medium heat 30 minutes or until mixture is reduced to 1 1/2 cups. Add sour cream, stirring until well blended. Slice roast, and serve with gravy.