Preheat the oven to the broil setting. Lightly grease a roasting pan or line it with aluminum foil.
Heat 1 tablespoon of the olive oil in a large skillet over medium heat. Add the green onions and rosemary, cooking for about 5 minutes until softened.
Stir in the garlic, mushrooms, spinach, and nutmeg. Cook for another 6 minutes until the mushrooms release their moisture. Remove from heat and stir in the cornbread crumbs, dried cranberries, 2 tablespoons of the apple cider, ½ teaspoon of the salt, and ¼ teaspoon of the pepper. Set the stuffing aside.
Butterfly the turkey breast so it lies flat. Season the meat all over with the remaining 1 ½ teaspoons of salt and ¾ teaspoon of pepper.
Spread the spinach and cranberry stuffing evenly over the flattened turkey breast. Starting from one of the long edges, roll the meat tightly into a log shape. Tie the roll with kitchen twine every 2 inches (5 cm) to secure it.
Brush the outside of the turkey roll with the remaining 2 tablespoons of olive oil and the melted butter. Place it in the prepared roasting pan and broil until the outside is browned, watching closely to prevent burning.
Change the oven temperature to 325°F (165°C). Combine the chicken stock and the remaining apple cider, then pour the liquid into the bottom of the roasting pan.
Cover the pan tightly with foil. Bake for 90 minutes, basting occasionally, until a meat thermometer inserted into the thickest part of the turkey registers 165°F (74°C).
Remove from the oven and let the turkey rest, loosely covered with foil, for 20 minutes. Remove the twine, slice into ½-inch to 1-inch (1.25-2.5 cm) rounds, and serve with the pan juices.