Preheat oven to 400 degrees. Line a baking sheet with parchment paper and set aside.
Toss the cauliflower florets with 1 tablespoons of olive oil. Season with sea salt and black pepper.
Spread the cauliflower out on the prepared baking sheet and roast in the oven for 30 minutes. Remove from the oven and set aside. Reduce heat to 375 degrees.
While the cauliflower roasts, heat a skillet over medium heat. Add 1/4 cup of olive oil and saute the mushrooms, onions and celery until mushrooms are soft, about 10 minutes.
Add the walnuts, garlic, thyme, parsley, sea salt and remaining 1/4 cup of olive oil to a large bowl. Toss to combine.
Next, add the roasted cauliflower and the sauteed mushroom mixture, toss to combine.
Finally, add the cooked sausage and toss it all together.
Pour the stuffing mixture into a large baking dish (mine is 9 1/2 x 11 1/2) a 2-quart casserole dish is too small.
Place in the oven and bake for one hour, stirring every 15 minutes to keep it from burning.
Remove from oven and serve.
Notes
Do not skip stirring the stuffing as it bakes. The ingredients on top will burn so they need to be turned over.
If you do not like sausage or cannot find a sugar-free version, substitute cooked bacon pieces or any meat that you like.