Add the cauliflower to a large mixing bowl, pour the olive oil and melted butter over the top, then toss to coat. Sprinkle 2 tablespoons of the ranch seasoning over the top and toss. Pour the cauliflower onto a baking sheet lined with parchment paper, and roast for 25 minutes.
While the cauliflower is roasting, combine the cream cheese, heavy cream and the remaining 2 tablespoons of ranch seasoning in the same mixing bowl and mix.
Add in half the cheddar cheese and chives, then mix. Once the cauliflower is done, pour the hot cauliflower over the cream cheese mixture and toss until well combined.