Preheat the oven to 400ºF. In a large rimmed baking sheet, toss the cauliflower florets and garlic cloves in the olive oil and arrange them into a single layer. Roast until fork-tender and golden, about 30 minutes.
Transfer the roasted cauliflower and garlic to a blender, and add in the water, salt, lemon juice, and nutritional yeast. Blend until very smooth. Adjust any seasoning to your taste, and then serve warm over your favorite vegetables, nachos, or baked fries.