Preheat oven to 425.
In a baking sheet toss together, the cauliflower olive oil, hot sauce, paprika, cayenne, garlic powder, and a pich of salt and pepper. Add the parmesan and toss to coat.
Transfer to the oven and roast for 15-20 minutes. Remove and add the cheddar.
Return to the oven and continue cooking for another 10 minutes, until the cauliflower is golden and the cheese begins to crisp.
Meanwhile, make the ranch. Combine all the ingredients in a bowl. Add 1/4 cup water and whisk with a fork to combine, adding water if needed to thin.
Taste and adjust seasonings. Serve the warm cauliflower bites with the tahini ranch.