Grease 2 large baking sheets with oil and evenly spread the turnips and sweet potatoes on them.
In a small bowl combine all of the seasonings and spices.
Sprinkle about half of the spice mix onto the veggies and toss until coated.
Put into the oven and roast for about an hour until they’re soft and starting to turn golden brown, tossing a few times to brown evenly.
While the turnips and sweet potatoes are cooking, brown the sausage over medium heat in a large skillet on the stovetop if you’re using it. Remove the sausage from the pan and leave the drippings.
Add the onion and celery to the skillet and saute. Add some of the tallow or coconut oil to the skillet as needed if you didn't have sausage drippings.
Once the onion and celery have started to soften, add the mushrooms and apple to the skillet and continue cooking until they’re all cooked.
Return the sausage to the skillet and add more of the spice mixture to taste.
Remove from heat.
Once turnips and sweet potatoes are done, mix with the sausage/onion/celery/apple/mushroom mixture and continue mixing until well incorporated and starting to clump together.
Transfer to a greased 9x13 baking dish and warm in the oven if serving immediately or put in the refrigerator, covered, if using later.
Notes
For reheating heat the covered casserole dish at 350° for 30 minutes. Store any leftovers in an airtight container in the fridge.