Preheat your oven to 425°F (220°C).
Cut off the top of each garlic head to expose the cloves. Place the heads on a sheet of aluminum foil, drizzle with olive oil, and wrap them tightly. Roast the garlic in the preheated oven for about 30-35 minutes or until the cloves are soft and golden brown. Remove from the oven and let them cool.
Meanwhile, in a large bowl, combine the cauliflower florets and carrot sticks. Drizzle with olive oil, lemon zest, lemon juice, salt, and pepper. Toss to coat the vegetables evenly.
On a separate baking sheet, spread out the seasoned cauliflower florets and carrot sticks. Place the roasted garlic heads on the baking sheet as well. Roast in the preheated oven for about 20-25 minutes or until the vegetables are tender and slightly browned.
While the vegetables are roasting, prepare the rest of the platter. Begin by placing three small dishes in a triangle pattern. Two dishes will be for dips, and one dish will be for olives. Place one small dish in the corner to hold your roasted veggies. Arrange the cucumber slices, cherry tomatoes, celery sticks, and broccoli florets on a large serving platter. Slot the flatbread and crackers in next to the dips.
Once the roasted vegetables and garlic are done, remove them from the oven and let them cool slightly. Place them on the dish reserved for the roasted vegetables.
Place the roasted garlic bulbs on the platter alongside the other vegetables.