1. Rub lamb with 2 tsp. salt and 1 tsp. pepper; let stand 1 hour.
2. Pulse rosemary in a food processor 4 or 5 times or until finely chopped. Add parsley and next 4 ingredients, and pulse 4 or 5 times or until finely chopped. Add 6 Tbsp. olive oil, and pulse 7 or 8 times or until smooth, scraping down sides as needed. Rub mixture over lamb; place in a large roasting pan. Let stand 30 minutes.
3. Preheat oven to 450°. Toss together potatoes and remaining 1 1/2 tsp. salt, 1 tsp. pepper, and 4 Tbsp. oil; place potatoes around lamb in roasting pan.
4. Bake at 450° for 50 minutes to 1 hour or until a meat thermometer inserted into thickest portion registers 125° (rare). Remove lamb from pan; cover loosely with aluminum foil, and let stand 15 minutes before slicing.
5. Dice half of lamb; package in 2 (2 1/2-cup) portions, and reserve for Rosemary Lamb Stew and Lamb Pita Pockets. Serve remaining lamb with potatoes and pan juices.
Note: Peel the centers of the potatoes for a pretty presentation, if desired.