Preheat the oven to 220°C.
Pound herbs, garlic, olive oil, salt, and peppercorns in a mortar to form a coarse paste.
Lay the lamb skin side down and slash the meat deeply.
Rub the herb paste into the cuts and lay sliced peppers on top.
Roll the lamb, tie with string, and wrap tightly in three or four layers of foil.
Bake the lamb for 1½ hours.
After 30 minutes, place potatoes, parsnips, carrots, garlic, lemon, and herbs on foil.
Season the vegetables, seal the foil bag, and bake with the lamb for the remaining hour.
Mix the juices from the lamb foil with flour, butter, and red wine to create a whisked gravy.