Step 1 Preheat oven to 200°C. Using a food processor, blend bread and parsley until they resemble fine breadcrumbs. Place into a bowl. Add tomatoes, capers and egg and stir to combine.
Step 2 Place lamb shoulder onto a flat surface, skin side down. Spread bread mixture over lamb. Roll up to enclose filling and secure with kitchen string. Place into a deep baking dish. Pour stock and 3/4 cup water over lamb. Cover with foil and bake for 45 minutes.
Step 3 Line a baking tray with baking paper. Arrange potatoes on tray. Spray with olive oil and roast for 45-55 minutes, or until potatoes are crisp and golden.
Step 4 Drain pan juices from lamb and set aside for the gravy. Cook lamb, uncovered, for a further 30-35 minutes or until golden. Place lamb onto a chopping board and cover with foil to keep warm.
Step 5 Heat baking dish over medium heat and add flour. Stir until well combined. Remove from heat and gradually add saved meat juices and water (about 1 cup), stirring to combine. Return to heat and cook, stirring, until gravy comes to the boil. Reduce heat and simmer for 2 minutes or until gravy thickens. Slice lamb. Serve with vegetables and gravy.