In the bowl of a food processor, combine the mint leaves, cilantro leaves, garlic, 1/2 teaspoon of the salt and 1/2 cup of the olive oil and pulse until herbs are finely chopped and thoroughly combined. Transfer to a nonreactive container and set aside.

Line a shallow baking dish or roasting pan with aluminum foil. Place the pork in the pan and rub evenly on all sides with 1 tablespoon of the remaining olive oil. Season well on all sides with the remaining 1 teaspoon of salt and the black pepper. Spoon 1/4 cup of the mint-cilantro mixture over the meat and, using your hands, rub well on all sides so that the herb mixture evenly coats the roast. Refrigerate mint-cilantro mixture until ready to serve. Drizzle the remaining 1/2 cup of olive oil over the herb mixture so that it forms a layer of oil over the chopped herbs (this will help the herbs from oxidizing while the meat is marinating.) Cover loosely with plastic wrap and set aside to marinate, refrigerated, for 3 hours.

Preheat the oven to 425 degrees F.

Remove the pork from the refrigerator and allow to come to room temperature for at least 1 hour before roasting. Remove the mint-cilantro sauce and set aside until ready to serve the pork.

Transfer pork to the oven and cook until lightly golden and an instant-read thermometer registers 140 degrees F, 30 to 35 minutes. Remove the meat from the oven and set aside to rest for at least 10 minutes before slicing. Serve the meat sliced in thin slices, stir the mint-cilantro sauce, and serve the meat drizzled with the sauce.