Make marinade: Grate the garlic cloves and give them to a small bowl. Add the dried oregano and 1 teaspoon of the dried rosemary. Add the lemon juice (reserve the juiced lemon halves for stuffing the chicken). Add 3 tablespoons of the olive oil, salt, and pepper. Stir well.
Marinate: Pat the chicken dry with kitchen paper (Note 1). Rub very well with the marinade, outside and inside as well. Cover with cling film and marinate for 2-3 hours in the fridge. Bring to room temperature before placing it in the oven, about 30 minutes.
Preheat the oven to 180 degrees Celsius/ 350 degrees Fahrenheit.
Prepare vegetables: Peel and cut the potatoes into large chunks. Peel and cut the carrots into sticks. Peel and cut the onion into wedges. Place them all into a large roasting pan. Pour the remaining olive oil (2 tablespoons) on top, add the remaining rosemary (1 teaspoon), fine sea salt, and freshly ground black pepper. Mix well with your hands so that the vegetables are evenly coated with the oil and spices.
Heat the chicken stock in a small pan and pour it into the roasting pan. Pour it carefully in one corner of the pan so that the spices covering the vegetables are not washed away. Shake the pan gently to distribute the stock all over the pan.
Tie chicken: Place the squeezed lemon halves into the chicken's cavity. Tie the legs of the chicken and place the chicken on top of the veggies.
Roast for 1 hour and 15 minutes or until the internal temperature of the chicken reaches 165 degrees Fahrenheit/ 73 degrees Celsius.
Check: If you have a kitchen thermometer, check the temperature by inserting the thermometer into the thickest part of the thigh. If you don't have a thermometer, pierce the chicken with a skewer in the thickest part of the thigh, the juices should run clear.If the chicken is not ready yet, return it to the oven and check again after about 5 more minutes. Repeat until the juices run clear or the internal temperature is reached.
Rest the chicken for about 15 minutes before carving (Note 2).
Don't wash the chicken before cooking. Washing the bird in your sink will only cause this bacteria to contaminate your sink and other surfaces.