Preheat the oven to 425ºF.

Cut the tip off the head of garlic, exposing the very top of the cloves. Drizzle the top of the garlic head with EVOO, wrap it tightly in tin foil. Place the garlic head in the oven and let it roast for approximately 45 minutes. When the garlic is finished and cool enough to handle, squeeze the cloves out of their skins and into a small bowl. Mash it with a fork.

Arrange the chicken pieces in a roasting pan, drizzle them with EVOO and season them with grill seasoning. Roast the pieces in the oven alongside the garlic, until they reach an internal temperature of 165ºF, about 35 minutes.

Toss the potatoes and broccoli separately with EVOO and grill seasoning, making sure that they are evenly coated. Transfer the vegetables to separate baking sheets and roast them in the oven, along with the garlic and chicken, until they are tender and crispy, 20-25 minutes.

Once the garlic, chicken, and vegetables are in the oven, melt the butter in a medium skillet over medium heat. Sprinkle the flour into the butter and stir the mixture, allowing the flour to cook slightly, about 1 minute. Whisk in the chicken stock, allowing it to simmer and thicken, about 3-5 minutes. Add the roasted garlic mash to the gravy, stirring to incorporate and season with salt and pepper to taste.