In a small bowl, combine salt, pepper, paprika, garlic powder, and onion powder.
Combine vinegar and tomato sauce in a small bowl. Set aside.
Season all sides of roast with spice mixture.
NOTE: You may have some of the spice mixture left over. This can be saved for another use.
Slice onion into thick slices and place in the bottom of the crock pot.
Warm oil in a large skillet over medium-high heat. Place roast in the skillet and brown one side, without moving the roast, for 5 minutes. Use tongs to flip the roast and brown the other side for 3 minutes. Brown the other parts of the roast for about 1 minute each side. Place browned roast on top of onion in crock pot.
Turn heat to low, add water and wine to the skillet. Deglaze pan with a wooden spoon. Pour pan liquid over roast, then pour balsamic mixture on top.
Place lid on crock pot and cook on low for 8 hours.
While roast cooks, steam cauliflower until tender. You can steam in a microwave by placing in a covered bowl with a little water and heating for about 2-3 minutes. You can also steam in a steamer insert over simmering water.
Drain cooked cauliflower and transfer to bowl of a food processor. Add butter and season with salt and pepper. Process until smooth.
NOTE: I had a turnip I needed to use so I cooked it and added it to the cauliflower. I think it improved the texture and flavor. If you have a white root vegetable, feel free to cook it and add it in.
When roast is done, shred it in its juices, serve over pureed cauliflower, and ladle juice over the top.