For the pork: Mix together the mustard and apple cider and brush all sides of the pork loin and ribs with the mixture. Liberally sprinkle the pork loin and ribs with the smoked paprika, 1 tablespoon salt and 2 tablespoons cracked black pepper. Add some oil to a cast-iron skillet or roasting pan, then place the rack of ribs, curved-side down, in the skillet and place the loin, fat-side up, on top of the ribs. Roast until the internal temperature of the loin reaches 145 degrees F, about 30 minutes.
While the pork begins to roast, cut the carrots, parsnips, potatoes and turnips into wedges using an oblique cut: Place a vegetable on a cutting board and hold your knife at a 45-degree angle to the vegetable. Cutting roughly 1-inch slices on the diagonal, roll the vegetable a quarter turn toward you each time you make a cut so you're cutting point to point until the vegetable is completely cut. Add the carrots, parsnips, potatoes, turnips, garlic and thyme to the skillet with the pork roast. Drizzle with some olive oil and sprinkle with salt and pepper. Return the skillet to the oven and continue to cook until the loin reaches 145 degrees F.
Transfer the pork loin to a cutting board to rest and tent with foil. Return the skillet to the oven and cook until the ribs and vegetables are cooked through, about 30 minutes.
Remove the skillet from the oven, transfer the vegetables to a platter and transfer the ribs to a cutting board.
For the pan gravy: Heat the same skillet over medium heat. Add the flour and whisk until it absorbs the fat in the skillet. Slowly whisk in the cider and 1 cup water and bring to a simmer, whisking constantly to smooth out any lumps, until the sauce thickens slightly, about 2 minutes. Stir in the parsley and set aside.
Cut the rack of ribs into individual ribs and scatter over the roasted vegetables. Slice the pork loin and shingle onto the platter. Spoon the pan gravy over the top and serve.