Preheat oven to 425°.
To prepare lamb, sprinkle lamb evenly with 3/4 teaspoon salt and pepper. Place lamb on a broiler pan coated with cooking spray. Bake at 425° for 21 minutes or until a thermometer inserted in thickest part of roast registers 120°. Place lamb on a cutting board; let stand at room temperature 10 minutes before slicing.
To prepare sauce, combine sambal oelek and next 4 ingredients (through garlic) with a mortar and pestle; grind into a fine paste. Slowly drizzle oil into sambal mixture, stirring until thoroughly combined. Serve sauce with lamb.