In a medium skillet, cook the bacon over medium-high heat until crisp. Transfer the bacon to a paper towel-lined plate to cool, and set aside. Reserve 1/4 cup of bacon grease.

Preheat oven to 425°F. Line a baking sheet with parchment paper. Set aside.

In a large bowl, combine the cauliflower, bacon grease, garlic powder, and black pepper. Toss to combine.

Spread cauliflower on the prepared baking sheet, and then bake in preheated oven for 18-22 minutes, flipping once halfway through. The cauliflower should be tender and golden brown when ready.

Sprinkle the cheddar cheese on top of the cauliflower, and bake an additional 2-3 minutes to melt the cheese.

Remove from oven, and top the cauliflower with the crumbled bacon and green onions, and drizzle on the ranch dressing. Serve immediately.