Preheat the oven to 400 degrees F. Fill of 9x13-inch baking dish with the cauliflower florets. Drizzle the olive oil over the top. Then roast in the oven for 20 minutes.
In the meantime, mix the milk, flour, sea salt, paprika, and nutmeg in a medium bowl. Whisk well to incorporate the flour then toss in the shredded cheese.
Once the cauliflower is out of the oven, pour the milk mixture over the cauliflower, and toss a little to allow the cheese to work down in between the cauliflower. Then mix the panko, melted butter, and thyme together in a small bowl. Sprinkle the panko over the top of the cauliflower. Then bake another 25-30 minutes until golden on top and bubbly around the edges. Serve warm.