Melt butter in a sauce pan, add salt, cinnamon, sugar and nutmeg and stir until smooth. Add remaining ingredients, cover and cook over low heat 15 minutes, stirring occasionally. Brush or marinate lamb ribs in sauce before grilling.
Rub lamb riblets with salt and pepper and thread on barbecue spit or place in crown on grill. Cook, 5 to 6 inches above coals for about 45 minutes or until well done. Brush with sauce every 15 minutes. Serve riblets with remaining sauce.