Remove the chicken giblets. Rinse the chicken inside and out. Remove any excess fat and leftover pin feathers.
Put the chicken in a container large enough to hold the chicken and brine, add enough water to cover the chicken first to gauge how much water will be needed before adding all the other ingredients.
Mix the salt, sugar, whiskey and spices in the water to dissolve. Submerge the chicken, cover and refrigerate overnight.
About an hour before roasting remove the chicken from the brine, pat dry with paper towels and set on a rack over a platter or roasting pan (to catch the drippings) in the fridge. This allows the skin to dry out a bit so that when you roast you can get nice crispy skin.
Roasting the Chicken
Preheat the oven to 425 degrees F.
Stuff the cavity of the chicken with most of the fresh thyme, rosemary, sage, lemon, 1/2 onion, and whole garlic cloves. Brush the outside of the chicken with the butter and sprinkle with a little salt and pepper (the brine adds saltiness, so do not use too much salt on the outside of the chicken). Place the onions, potatoes, celery and carrots, in a roasting pan. Toss with salt, pepper, fresh thyme, rosemary and olive oil. Spread around the bottom of the roasting pan and place the chicken on top.
Roast the chicken for 45 minutes uncovered until the skin browns, then lower the oven temp to 375 and tent the chicken with aluminum foil. Continue to roast another 45 minutes, or until the juices run clear when you cut between a leg and thigh (internal temperature should read around 150 on an instant read thermometer - the carryover heat will bring it up to around 160 while it rests).
Remove the chicken and vegetables to a platter and cover with aluminum foil for about 20 minutes to allow the chicken to rest and the juices to redistribute. Slice the chicken onto a platter and serve it with the vegetables.