Heat oven to 400° Line a baking sheet with parchment paper or foil.
In a microwave safe bowl, melt butter, olive oil and garlic together. Add cauliflower florets. Toss to coat.
Place butter coated cauliflower on the prepared sheet pan. Sprinkle with kosher salt. Roast for about 20 minutes. Toss to rearrange the cauliflower and roast an additional 10 minutes or until cauliflower is tender and golden brown.