Preheat the oven to 300˚F.
Line a rimmed baking sheet with foil, lay out the rack of ribs and sprinkle with salt. Cover with another piece of foil and roast for 3–3 1/2 hours, or until the meat is very tender. (If you like, pour the fat off the bottom of the pan into a ramekin and save it in the fridge to start a sauce or stew or roast potatoes or vegetables.)
Increase the oven temperature to 425˚F and if you like, cut potatoes, broccoli, cauliflower or other vegetables into large chunks and toss in a drizzle of oil to coat.Spread on the pan around the ribs.
Stir the maple syrup, mustard, vinegar and rosemary in the same bowl, and brush over the ribs.
Return to the oven for 20-30 minutes, or until the ribs are sticky and caramelized and the veggies are tender and golden.