Rinse the chicken and pat dry. Peel the potatoes and cut into quarters, lengthwise. Salt and pepper the chicken and potatoes. Transfer chicken to a roasting pan, and add potatoes, on and around the chicken. Add oregano, garlic, olive oil, and lemon juice, distributing evenly across the pan. Add water and roast uncovered at 355°F for a total of 1 hour and 40 minutes. Half way through (50 minutes), turn the chicken.