Once you’ve defrosted a roast, you have up to five days to cook it. Any longer than that and the freshness and quality of the meat suffers. If you keep the roast too long before cooking it, you risk food poisoning.
Keep it Cool
Store a defrosted roast in a refrigerator set at 40 degrees Fahrenheit or below. While the cold temperature will slow the growth of bacteria that causes food poisoning, it won’t eliminate it. If you realize one or two days into the defrosting process that you won’t be able to cook the roast, you can refreeze it if it still has ice crystals. Once it’s completely defrosted, you can still stick it back in the freezer as long as no more than 24 hours have passed since the ice crystals have all melted.