In skillet over medium-high heat, cook leeks and garlic in olive oil for 3 minutes. Stir in spinach and 1/2 teaspoon each of thyme and oregano. Cook 5 minutes or until spinach is wilted.
Remove from heat. Stir in raisins, peppers and cheese. Season with salt and pepper, if desired.
Open pork like a book; spread with spinach mixture, leaving 1-inch border. Roll jelly-roll style; tie at 1-inch intervals. Place pork on rack set in roasting pan. Sprinkle with remaining thyme and oregano. Season with salt and black pepper, if desired. Roast at 425 for 20 minutes.
Reduce heat to 350°; cook 40 minutes more, or until thermometer inserted in meat reads 150°.