1. Preheat the oven to 375 degrees F.
2. To prepare the chickens, in a small bowl, combine the butter, thyme leaves, parsley, and lemon juice and zest and mix well. Rub the herb butter under the skin of the breast and over the meat of the chickens. Season all over with the salt and pepper.
3. Tuck the wing tips under the backs of the chickens and use kitchen twine to tie the legs together. Put the onion, carrots, celery, thyme sprigs, and wine in a large roasting pan. Cover with a roasting rack and place the chickens on the rack breast side up. Roast in the center of the oven until the chickens are golden brown, their skin is crispy, and a thermometer inserted into the thickest part of the thigh joint registers 165 degrees F to 170 degrees F, about 1 hour 15 minutes. Discard the onion, carrots, celery, and thyme.
4. While the chickens are roasting, make the potatoes. In a small bowl, combine the salt, pepper, garlic, onion, oregano, and paprika and mix well. Spread the potatoes evenly on two large rimmed baking sheets and drizzle them with the olive oil. Sprinkle the spice mixture over the potatoes and shake the pans to coat evenly. Roast, turning the potatoes halfway through cooking, until tender when pierced with a knife and browned in spots, about 45 minutes.
5. To prepare the cauliflower, remove the outer green leaves from both heads, leaving the cores intact. Place one cauliflower head on its base on a cutting board. Using a sharp knife, cut it into 1-inch, bite-size florets. Transfer the florets to a large bowl. Repeat with the other cauliflower. Add the olive oil, salt, black pepper, garlic, onion, parsley, and chili flakes and toss until well coated. Spread the cauliflower evenly on two large rimmed baking sheets. Roast until tender and golden brown around the edges, 20 to 25 minutes.
6. Transfer one roasted chicken to a platter, tent loosely with aluminum foil, and let stand for 15 minutes. To serve, carve the chicken into 10 pieces and serve with half of the roasted potatoes and cauliflower.
If you can¿t fit everything in your oven at the same time, just hold back about half of the potatoes and cauliflower and roast them while you eat dinner.
"Guy Fieri Family Food" by Guy Fieri (c) William Morrow 2016. Provided courtesy of Guy Fieri. All rights reserved.