Preheat oven to 190°C (375°F).
Carve the pork rind with a sharp knife in a diamond shape pattern, then wrap the loin with it. Secure it with butcher's twine.
Season the meat with salt, ground black pepper and cumin, and rub it thoroughly.
Cover with extra virgin olive oil the bottom of a pan, heat it over medium heat and brown the meat on every side, then transfer it into a baking pan.
Now prepare the vegetables that will go around the meat. Cut the onion into wedges, wash and peel the carrots and celeriac, cutting them in chunks.
Place the vegetables and the garlic around the meat, season with extra virgin olive oil, salt and pepper and roast the meat in the oven for 20 minutes.
After 20 minutes, take out the meat, pour over the beer and stash it back in the oven, roasting it for about two hours.
Now the meat will be almost ready, you just have to brown the rind.
Turn up the oven to 210°C (410°C), and baste the meat with the cooking juices.
Roast the pork for the last 20 minutes, basting it often.
Now remove the meat from the oven and keep it warm. Serve it cut in slices, dressing it with its cooking juices.