Combine the garlic, rosemary, oregano and olive oil in a large shallow dish. Stir well to combine. Add lamb and turn to coat in marinade. Cover and refrigerate for 30 minutes.
Heat BBQ grill plate over high heat. Grill capsicum, skin side down for 10-12 minutes or until skin is blistered and blackened. Remove and allow to cool. Peel skin from capsicum. Cut flesh into thin strips.
Heat BBQ hot plate over high heat. Cook lamb for 8-10 minutes on each side for medium rare or until cooked to your liking. Cover and rest for 10 minutes.
Meanwhile, reduce grill plate heat to medium. Add tomatoes and asparagus. Cook tomatoes for 2-3 minutes or until tender and cook asparagus for 2-3 minutes or until cooked to your liking.
Heat a frying pan over medium-high heat. Add the pine nuts and cook, stirring occasionally, for 3-4 minutes or until toasted. Remove and set aside. Add butter and lemon juice to the pan, stirring until butter has melted.
To serve, arrange roasted vegetables on a plate, top with sliced lamb. Drizzle with butter sauce and scatter with pine nuts.