Preheat the oven to 425°. In a large roasting pan, heat the olive oil over moderately high heat until shimmering. Season the chicken legs with salt and pepper. Add them to the roasting pan, skin side up, and cook over moderate heat until golden on the bottom, about 5 minutes. Transfer the chicken to a platter. Add the mushrooms and leeks to the pan and cook until just beginning to soften, about 1 minute. Add the wine, paprika and rosemary. Return the chicken legs to the pan, skin side up, and roast in the oven for 45 minutes, or until the chicken is cooked through.