Blend tomatoes, onions, green pepper, lemon juice, oil, and all spices until smooth.
Rub the marinade thoroughly inside and outside the chickens.
Cover and refrigerate for at least 2 hours or overnight.
Slice potatoes and carrots; toss with remaining marinade, garlic, bay leaves, and pepper.
Stand each chicken upright on a clean glass bottle in a large roasting pan.
Arrange vegetables around the bottles and add hot water to one-quarter height.
Roast at 200°C (400°F) for 75–90 minutes until skin is deep golden and internal temperature reaches 75°C.
Rest 5 minutes, then carefully remove from bottles and serve with the vegetables.
Tip: Overnight marinating gives the best flavor and juiciness.
Tip: Use sturdy bottles that fit snugly inside the chicken cavity.