Wash and pat dry your hem. Let sit for 15 minutes.
Preheat oven to 400.
Cut onion into 6 pieces and add to an aluminum roasting pan.
Cut the carrots into about the size of the potatoes. Add potatoes and carrots, salt, pepper, garlic, thyme, and 3 tbsp olive oil to the roasting pan.
Trim the ends of a lemon, and cut into quarters. Stuff the chicken with the lemon, salt, and pepper.
Using cooking twine, start wrapping underneath the wings, then wrap around the back, cross each wing and bring twine across the front, cross the twine, bring it back down, cross the twine over the top of the leg, then under the breast. Turn the chicken over and tie the twine. Cut off any excess.
Coat the chicken with 2 tbsp of olive oil and dijon mustard. Place the hen on top of the vegetables in the roasting pan.
Cook at 400° for 1 hour and 30 minutes. Serve immediately.