Pat the pork loin dry with paper towels. This helps to achieve a crispy crackling.
In a small bowl, mix together olive oil, salt, black pepper, garlic powder, onion powder, rosemary, and thyme.
Rub the spice mixture all over the pork loin, ensuring it's evenly coated.
If using, toss the potatoes and carrots with a little olive oil, salt, and pepper and place them in the bottom of a roasting pan.
Place the pork loin, fat-side up, on top of the vegetables (or directly in the roasting pan if not using vegetables).
Roast for 20 minutes at 400°F (200°C).
Reduce the oven temperature to 350°F (175°C) and continue roasting for approximately 25-30 minutes per pound, or until an internal thermometer registers 145°F (63°C) in the thickest part of the roast.
For the last 15-20 minutes of cooking, you can increase the oven temperature back to 400°F (200°C) to help crisp up the crackling, watching carefully to prevent burning.
Once cooked, remove the pork roast from the oven and let it rest for at least 15-20 minutes before carving. This allows the juices to redistribute, resulting in a more tender and moist roast.
Serve the pork roast with the roasted vegetables (if used) and your favorite gravy.
Notes
For an even crispier crackling, score the fat layer before rubbing with the spice mixture. If you find the crackling isn't crisp enough, you can briefly place it under the broiler at the end of cooking, watching very closely.