Ok, I would unroll it. Put it in a non metallic dish, pat it down with kitchen roll and then make sure it is nicely scored along the top.if it isn't use a REALLY sharp knife or even better, a Stanley knife to score it. Remember, try not to cut into the flesh of the meat, just score the ski a nd fat underneath.
Then rub a shit load of sea salt into the skin. I would use a teaspoon for a piece 1 kg. put it in the fridge overnight - and don't cover it. You want the skin to dry out.
Next day, put your oven on HIGH and get it nice and hot. Take your pork out of the fridge whenyounturn the oven on to get up to room temp. At this point I make a ' trivet ' for the pork. Roughly chop any of the following - celery, carrots, onion and put the pork on top of this. Shove some thyme on two if you have any.
Then put pork InThe oven. Leave it for 30/40 mins until the top goes bubbly. When it has done this, turn the oven down and pour some water/ stock / wine into dish and cover with foil. I then cut a hole in the top of the foil so the skin is still exposed . Cook on a low oven for two hours- check it and see if a knife slides into the flesh like butter. If it doesn't , put it back in. There's no set time at which it will be done as every piece of pork is different. I have had pieces done in 90 mins, others have taken 4 hrs!! If the top is not crackly enough put the grill on and shove it under there but watch it carefully!! Now, take the pork out and leave it to rest for twenty mins. Get a fork and mush up all of the veg into the juice InThe bottom of the roasting dish. Now sieve it all squishing down as you put the veg in the sieve. This juice can be the basis of your sauce and it will be divine- or you can just use it as a jus. Hope this helps xxx