Preheat your oven to 425 degrees F. Line a rimmed baking sheet with parchment paper, for easier cleanup.
If the cauliflower is wet (from thawing from frozen or washing), pat it dry as best you can.
In a medium bowl, mix together the flour (1/2 cup), milk (3/4 cup), kosher salt (1 teaspoon), and black pepper (1/2 teaspoon) until well combined. I like to use a whisk for this so it's very smooth.
In a small bowl, melt 2 tablespoons of the butter. Add the panko breadcrumbs (1.5 cups) and stir to coat in the butter.
Add the cauliflower to the milk mixture and stir gently to coat every piece. Make sure every piece is very well-coated, and allow it to sit in there for at least 30 seconds.
Coat each piece of cauliflower in the panko breadcrumb and butter mixture, making sure to coat very well, and place on the prepared baking sheet. (Tip: I like to get the cauliflower from the bottom of the bowl, so it's really coated in the milk and flour batter, which helps the panko stick better.)
Bake at 425 degrees for 20 minutes.
Meanwhile, make the buffalo sauce by melting the remaining 2 tablespoons butter in a pyrex measuring cup, or a small bowl. Mix in the hot sauce (1/2 cup) and honey (1 teaspoon).
After the cauliflower has roasted for 20 minutes, pour the buffalo sauce on top, toss to coat, and spread back out on the baking sheet. Roast for another 10 minutes at 425 degrees.
Serve with celery sticks and ranch or blue cheese dressing, if desired. You can also mix up a little more buffalo sauce to drizzle on top if you want.