In a large bowl, toss cauliflower florets with melted butter, salt, and pepper and transfer to a small 1.5-quart casserole dish in a single layer.
Roast in the preheated oven for 15-20 minutes, until crisp-tender.
In another bowl, whisk together the sour cream and heavy cream, until smooth.
Add minced garlic, 1 cup shredded cheddar cheese, half of the chopped cooked bacon pieces, half of the green onions, plus onion powder, paprika, mustard powder, and ranch powder. Season with salt and black pepper and stir to combine.
When the cauliflower is done roasting, add it to the bowl with the sauce and mix it to combine it and coat it well.
Return the cauliflower mixture to the casserole dish. Top with the cream cheese pieces and any remaining cheese and bacon bits.
Bake for 5-10 minutes, until the cheese melts. Top with remaining green onions and serve.