Can I safely serve raw beef roasts that were left out to thaw for several hours? [duplicate]

No, you can not safely eat it. See answers to "Can I safely cook a steak that was left out raw for 7 hours".

Thawing at room temperature in air allows the surface to reach and maintain an unsafe temperature for some time, even as the interior remains quite frozen.

The appropriate ways to thaw the roasts are to do it in the fridge, or fully immersed in a bowl of COLD water with a trickle of cold water running over it. Thawing in water is the faster approach, and often takes under 30 minutes. It is safe to use this method for thawing requiring for up to 2 hours, but if considerable preparation is required, an hour is a better rule of thumb.

These are the approaches endorsed by cooking schools and health boards.

It's almost impossible for the answer here to be "yes", because the penalty for failure is fairly high. The "safe" answer of course is just "no" - since it can never be proved wrong. On the other hand, leaving meat out of the fridge (or freezer) to defrost is, I would suggest, a fairly common behaviour.

As with many things though, some common sense does apply. There are a number of factors to consider - and then at the end of the day, it's up to you.

a) the source of the meat. You may live in a country where all the meat comes in small polystyrene trays wrapped in cling-film. Where it's been immaculately handled from slaughter to supermarket. On the other hand many (dare I say most?) people buy meat that's been slaughtered right there in the market, and left all day under a hot sun, and endless flies. Quite surprisingly, they haven't all died. The former I'm somewhat more casual about than the latter.

b) the cooking method - "solid" beef, ie not ground beef, develops bacteria on the outside, not the inside. So I'd definitely give the outside of the meat a good searing to be sure. Or, if you like, slightly trim the outside of the meat first, then sear it.

c) slightly aside - the meat type. Beef (and lamb) are pretty resistant to spoilage - things like chicken and pork less so. Also chicken and pork can develop nasties "inside" the meat - one reason those meats are never served raw (or rare). Shellfish is also dangerous if it has spoiled.

d) the temperature of the room it was sitting in. If it's 110 in the shade outside, and like 90 in your kitchen, then 16 hours is a long time. In winter though I can leave a joint out overnight in the kitchen and it's still partially frozen in the morning. Clearly the temperature will affect the amount of time I'd leave it out for.

e) any obvious sign of spoilage? With beef (given that it doesn't really show) any unpleasant odor or color is probably not good.

At the end of the day it is your decision.