Toss cauliflower with olive oil, salt, and pepper in a large bowl.
Spread cauliflower on a baking sheet in a single layer; roast for 10 minutes. Flip cauliflower and bake for an additional 5 to 10 minutes, or until browned on bottom.
While cauliflower is roasting, melt butter in a small saucepan over medium heat.
Add garlic to butter and cook until fragrant (about 30 seconds to 1 minute), then mix in hot sauce and sriracha. Bring to a boil, then remove from heat. Set aside.
When cauliflower is finished roasting, place in a large bowl and toss with buffalo sauce.
Return cauliflower to baking sheet, then roast for an additional 5 to 7 minutes, or until hot and browned. Set aside.
Reduce oven heat to 425 degrees.
Prepare Mac and Cheese:
Coat a large baking dish (such as a 9 x 13-inch pan) with nonstick spray. Set aside.
Bring a large pot of salted water to a boil; cook fusilli until al dente. Drain and set aside.
While the pasta is cooking, heat the milk (in a microwave or small pot) until warm. Set aside.
Melt the butter in a large pan over medium heat, then add the garlic and cook until fragrant, about 30 seconds.
Add the flour, paprika, and cayenne to the butter and cook, then cook (stirring constantly), for a couple minutes.
Slowly add the warm milk, whisking to avoid lumps. Simmer mixture until thickened (it should coat a spoon), then whisk in cheddar cheese until smooth.
Remove sauce from heat. Season generously with salt and pepper.
Stir pasta into cheese sauce.
Transfer ½ the pasta to the baking dish; top with ½ the cauliflower, followed by ½ the blue cheese. Repeat layers one more time.
Bake at 425 degrees until hot and lightly browned on top, about 20 to 25 minutes.
Serve hot, sprinkled with additional blue cheese, if desired. Enjoy!
Notes
Time Saving Tip: Working on all the components simultaneously will keep things moving along faster. So start the cauliflower, then make the buffalo sauce while the cauliflower roasts. Once you get the cauliflower / sauce going, start cooking the pasta. And while the pasta is cooking make the cheese sauce. Hate Blue Cheese? If you're not a blue cheese fan, feel free to leave it out, serve it on the side, or replace it with another cheese, like feta. You could also drizzle the finished dish with Ranch Dressing, if you'd prefer.