Preheat the oven to 365 degrees F.
Combine the first 6 ingredients. Toss with the sweet potatoes. Place the sweet potatoes in a single layer on a sprayed baking sheet. Roast for 20 to 25 minutes until beginning to brown.
Combine all ingredients in a food processor or blender and puree.
Goat Cheese Sauce:
Combine the goat cheese and half-and-half in a small saucepan and heat over low heat until goat cheese is melted and sauce is warm.
Preheat a grill or grill pan over high heat.
Season the lamb with the salt and pepper. Grill to desired doneness, about 3 minutes per side for medium rare.
To serve, divide the sweet potatoes onto 4 plates, loosely stacking them towards the center. Position a lamb chop on each stack. Drizzle pesto around the potatoes. Spoon goat cheese sauce over lamb.