Preheat the oven to 425°F. Line a baking sheet with foil.

In a medium bowl, toss together the cauliflower florets with the olive oil and a pinch of salt and pepper. Arrange the cauliflower in a single layer on the baking sheet and roast it until it's golden brown, about 30 minutes, flipping the florets once halfway through.

Remove the cauliflower from the oven and transfer it to a food processor. Add the cream cheese, mayonnaise, sour cream, 1 cup Parmesan cheese, garlic, scallions, 1/2 teaspoon salt and 1/4 teaspoon pepper. Process the mixture until it is smooth and creamy. Transfer the mixture to a 10-inch skillet or an 8-cup baking dish. (See Kelly’s Notes.) Top the dip with the remaining 1/2 cup Parmesan cheese. Reduce the oven to 350°F and bake the dip until it is golden brown on top and the cheese is melted, about 20 minutes.

Remove the dip from the oven, garnish with additional scallions, and serve it immediately with assorted crackers or vegetables for dipping.

The dip can be prepared up to the baking step and stored, covered with plastic wrap, in the refrigerator up to 1 day in advance. When ready to serve, remove the dip from the oven and bake it as directed until it is golden brown on top.

The dip can be baked in several smaller skillets/baking dishes or one larger one.