In a bowl, toss the oil, garlic, cumin, cauliflower and toss to incorporate. Adjust the seasonings with salt and black pepper. Transfer the mixture to a baking dish, and dollop the top with little pats of the butter. Sprinkle the panko bread crumbs over the cauliflower. Roast the baking dish in the oven for approximately 20 to 30 minutes, or until the cauliflower is golden brown, and tender.