Preheat oven to 400 degrees Fahrenheit.
Spread bacon out on a large baking sheet (preferably a half sheet [like this]). Bake until done, about 10 to 20 minutes, depending on thickness.
Remove bacon to plate, and set aside. Keep pan with fat.
Spread out cauliflower on pan with bacon fat. Sprinkle with sea salt and optional pepper. Toss well with two spoons, so cauliflower is well-coated with fat. (*At this point, if you wish to make a one-pan dinner with roasted chicken, see instructions below in Recipe notes.)
Roast cauliflower about 22 minutes, or until tinged with brown on its edges.
Remove pan from oven. Add green onions' whites and optional cheese. Reduce oven temp to 200 degrees.
Put back in oven for 5 minutes. Chop bacon.
Remove from oven. Transfer to serving dish or individual plates. Top with chopped bacon, green onions' greens and lots of fresh thyme. Serve.
Also serve with optional fried/poached eggs (not for AIP) or roasted chicken for additional protein.