Preheat oven to 400 degrees. Place foil across a small baking sheet. Lay asparagus spears flat, drizzle with olive oil, a squeeze of the lemon juice, and season with salt and pepper. Place lemon slices and sprinkle pine nuts across asparagus. Roast in oven for 15-20 minutes, or until desired doneness. Garnish with freshly grated manchego cheese, serve.