Preheat your oven to 200°C/180°C fan (400°F/350°F).
Place your cauliflower florets and sausages in a large roasting tray. Drizzle with half of the oil and roast for 20 minutes, tossing halfway through.
Meanwhile bring a large pan of salted water to a boil. Cook the pasta until al dente. Drain.
Whilst the pasta is cooking heat the rest of the oil in a medium sized frying pan. Add the mushrooms and fry until soft, around 5 minutes. Set aside.
Next make the cheese sauce. Melt the butter in a medium frying pan on a medium-high heat. Once melted add in the onion and fry until soft, around 5 minutes. Add in the garlic and sage and fry for a further 2 minutes until fragrant.
Add in the flour and combine well with the onions. Fry for around 30 seconds. Pour in your milk, a little at a time, stirringly constantly until completely combined. Once thickened stir in the grated cheddar cheese. Season to taste with salt and pepper, set aside.
Once everything is cooked cut your sausages into 1-2cm(0.5-1inch) slices.
Preheat the grill to high.
Add the pasta, sausages, cauliflower and mushrooms into a large oven-proof dish. Stir to combine. Pour over the cheese sauce and stir to coat everything evenly.
Sprinkle the blue cheese, evenly place the Camembert slices and dot small splodges of cranberry sauce on top of the pasta bake.
Place the dish under the grill until the cheese is golden and bubbling.
