Slice the fennel bulbs into 1 × 1½-inch strips. Make slits over the whole surface of the roast and insert a strip of fennel and a little of the fennel or anise seed into each cut. Rub the roast with 1 teaspoon of the sage, salt, and pepper. Place it in a bowl and add the wine. Let it stand overnight, turning it over once.
The next day, remove the roast from the marinade and rub it with more salt and pepper, 1 teaspoon of the sage, and the remaining fennel or anise seed. Bind it securely with a string.
Preheat the oven to 400°. Oil a roasting pan and add the peanut oil. Place the pork in the pan and roast for 15 minutes. Reduce the temperature to 375° and cook for 1½ hours. Transfer the roast to a warm platter and let it stand for 5 minutes. Remove the string and slice it.
Pour the marinade into the pan and cook for 2 minutes over high heat, scraping the bottom with a fork. Add anise extract or Pernod and pour over the carved slices of pork. Sprinkle with fennel leaves and serve.