Preheat oven at 425 degrees Fahrenheit (220 degrees Celsius).
Rub salt and pepper into the chicken.
Push under the skin of each piece I piece of lemon and 2 garlic clove halves.
Place chicken on a large pan (large enough to fit potatoes and carrots in one layer).
Cut potato and carrots in smallish pieces 1 ½ -2 inches and put in a bowl along with sliced onion.
Add 4 tablespoon olive oil to the vegetables, pepper, and the oregano and mix well, until all vegetables are coated well.
Spread vegetables around the chicken.
Brush chicken generously with olive oil on both sides, roast skin facing up.
9. Roast for about 45 minutes-1 hour (if you are roasting a whole chicken it will take longer about a ½ hour more).
Check chicken, juices should be clear, although I prefer a meat thermometer, temperature at thickest part should be 165 F (74 C).
If chicken is done, but vegetables are not, remove chicken and cover with aluminum foil, and roast until vegetables are crunchy on the outside and soft on the inside.