How long to cook 2.2kg round roast fan oven?

For a 2.2 kg round roast in a fan oven, cook it at 180°C (350°F) for approximately 20-25 minutes per 500g for medium-rare. This means the total cooking time will be around 1 hour and 30 minutes to 1 hour and 50 minutes. Always use a meat thermometer to ensure the internal temperature reaches at least 63°C (145°F) for medium-rare. Let the roast rest for about 15-20 minutes before slicing to retain its juices.