Heat grill. Heat 1 tablespoon oil in medium saucepan over medium heat until hot. Add onion and garlic; cook 3 minutes or until onion is tender, stirring occasionally. Add roasted peppers, broth, 1/4 teaspoon salt and 1/8 teaspoon pepper; stir gently to mix. Cover; cook 5 minutes.
Transfer roasted pepper mixture to blender container or food processor bowl with metal blade; cover and blend until smooth.
Spray grill basket with nonstick cooking spray. Place scallops in grill basket. Brush scallops with 2 teaspoons oil; sprinkle with rosemary, 1/4 teaspoon salt and 1/4 teaspoon pepper.
When ready to grill, place grill basket on gas grill over medium heat or on charcoal grill 4 to 6 inches from medium coals. Cook 5 to 6 minutes or until scallops are opaque, turning once.
To serve, place about 1/2 cup sauce on each individual serving plate. Spoon scallops over sauce. If desired, garnish with fresh rosemary sprigs.