Preheat the oven to 400°F. Line a baking sheet with parchment paper and toss cauliflower florets with olive oil. Spread them in a single layer on the baking sheet and roast for 20 minutes until fork tender. Remove from oven and reduce the temperature to 350°F.

In a mixing bowl, combine sour cream, cheddar cheese, melted butter, and dry ranch seasoning. Adjust seasoning to taste.

Toss the roasted cauliflower in the cheese mixture until well-coated.

Transfer the cauliflower mixture to the prepared baking dish. Bake for 20 minutes until the cheese is melted and the edges are golden brown. Serve hot.