Preheat the oven to Gas Mark 5,190ºC (375ºF). Open out the pork onto a clean work surface and season generously. Sprinkle over the chopped rosemary, cheese, garlic and parsley in an even layer. Tightly roll the pork back up to enclose the filling completely.
Tie with string at 2cm intervals to keep the meat in shape. If the skin is not already scored, use a small sharp knife to score the skin between the strings. Wipe off any excess moisture with kitchen roll and sprinkle with salt.
Place in a roasting tin and roast for 20 minutes per 500g plus 20 minutes. For the last 20 minutes of cooking time, increase the oven temperature to Gas Mark 7, 220ºC (425ºF), so, if the joint is exactly 2kg, it will take one hours and 40 minutes until cooked through and tender with crispy crackling.
Leave the roast pork to rest in a warm place for 30 minutes, as it is actually best served warm. Carve into thin slices and arrange on warmed plates with the potatoes and baby carrots. Spoon over the pan juices to serve.