Fill your sink with water and soak the lid of the clay roaster for 15 minutes.
Mix 3 tablespoons of olive oil with 2 teaspoons of paprika and 1 teaspoon of both salt and pepper.
Toss vegetables with oil mixture
Drizzle 1 tablespoon of the oil mixture over 8 cups of chopped root vegetables, such as onions, potatoes, parsnips and sweet potatoes, and some fresh rosemary. Reserve the rest of the seasoning mixtures. Put the vegetables in the bottom of the clay roaster. Tuck a head garlic with the top cut off in with the vegetables.
Pat chicken dry
Using paper towel, pat chicken dry.
Rub chicken with oil
Rub 1 tablespoon of the seasoning mixture onto the chicken. Reserve the rest of the seasoning mixture.
Place chicken in roaster
Put the seasoned chicken on top of the vegetables and put the lid on the roaster.
Put roaster in oven
Place the roaster in the cold oven and turn the oven to 400°F. Roast for 1 hour.
Season brussels sprouts
Toss 2.5 cups of trimmed, halved Brussels sprouts with the remaining seasoning mixture.
Add sprouts to roaster
Add the seasoned Brussels sprouts to the roaster and return to the oven for 30 more minutes, or until juices from the chicken run clear.
Let meat rest
Remove roaster from oven and let it rest with the lid on for 10-15 minutes.
Squeeze garlic and toss vegetables
Carefully transfer the chicken to a plate. Squeeze the roasted garlic onto the vegetables and toss them all together.
Carve chicken and serve
Carve the chicken and arrange it on top of the roasted vegetables. Sprinkle with parsley and serve.