How long does a roast need to rest? December 22, 2021 20:52 Updated For the juiciest meat and most even cooking, let big roasts rest a full 30 minutes. But aim for at least 20 minutes for any size roast. Related articles How do I connect/pair the Smart Thermometer to my phone? Inaccurate results Quick start guide Can I air fry? What are the temperature limits?