The length of time a roast can stay in a slow cooker depends on the size of the roast, the specific recipe, and the setting you use. In general, most slow cooker recipes for roasts recommend cooking them on the low heat setting for 8 to 10 hours or on the high heat setting for 4 to 6 hours. However, these are just guidelines and may vary depending on the type of meat, the size of the roast, and the desired level of tenderness.
If you cook the roast for too long, it can become overcooked and dry. It's essential to monitor the cooking process, especially if you're using a slow cooker for the first time or trying a new recipe. It's generally best to follow a specific recipe for your chosen cut of meat and use a meat thermometer to check the internal temperature to ensure it's cooked to a safe level.
If you need to cook the roast for an extended period beyond the recommended time due to scheduling or other reasons, you can keep it on the "warm" setting, if your slow cooker has one, to maintain a safe temperature without overcooking the meat. However, it's not recommended to leave the roast in the slow cooker indefinitely, as food safety guidelines suggest that cooked meat should not be left at room temperature for more than two hours.
Remember, the best way to achieve a delicious and tender roast in a slow cooker is to follow a trusted recipe and be mindful of the cooking time and temperature to get the desired results.