Preheat the oven to 450°. In a very large roasting pan, toss the kale, potatoes and onion with the olive oil. Season with salt and pepper and spread in an even layer.
Set the chicken on a cutting board, skin side down. Slice halfway through the joint between the drumsticks and thighs. Season with salt and pepper, sprinkle with the paprika and set on top of the vegetables.
Cover the pan with foil. Roast the chicken in the upper third of the oven for 20 minutes. Remove the foil and roast for 30 minutes longer, until the chicken is cooked through and the vegetables are tender. Transfer the chicken to plates and spoon the vegetables alongside. Serve with lemon wedges.