Season lamb shoulder with sea salt and freshly ground black pepper. Heat 2 tbsp of oil in a large pan over high heat and cook lamb for 5 minutes, turning once, until browned. Transfer to a large roasting tin. Meanwhile, deglaze pan with red wine and stock then pour over lamb in roasting tin. Cook in a preheated oven at 220C for 20 minutes then reduce heat to 160C and cook for 3-4 hours until tender, basting occasionally and adding the truss tomatoes during the last 30 minutes of cooking.
For roast vegetables, combine ingredients in a bowl with remaining olive oil and season with sea salt and freshly ground black pepper. Place in another roasting tin and pour 1 cup water over. Roast in the oven for the last 2 hours while lamb shoulder is cooking. Serve lamb with truss tomatoes and roast vegetables on platters or plates.