Don't have time to bring meat to room temp
I am having guests tonight and got stuck at work--so I wasn't able to take my marinating pork shoulder out of the fridge. The thing takes three hours to cook---and I don't have time to let it get to room temp. What to do? Is there a way to counterbalance in oven? THANKS!
ipsedixit is on the right track. Assuming your refrigerator temperature is 40 degrees F (+/-) and ambient room temperature is 75 degrees F, your refrigerated meat will reach room temperature quickly. I'm not sure I agree with the 10 - 15 minute estimate (especially for internal temperature) but it will, nevertheless, warm quickly.
That said, why does your meat need to be at room temperature when it enters the oven.
For purposes of discussion, let's say you put a 40 degree roast into a 350 degree oven for five minutes, I can assure you that it will reach "room" temperature by the end of that time. It's only about a 35 degree increase in temperature. So, you've added five minutes to your cooking time; negligible.
If you're truly concerned about it, start your 40 degree roast in an oven that's 25 degrees hotter than you intend to cook the roast. After 5 - 10 minutes, turn the heat down to your preferred roasting temperature.
To strive for starting temperature accuracies above freezing that differ by only about 35 degrees is ludicrous.
Your easiest solution is to just cook the meat an extra half-hour or so. If this were a different cut -- such as a prime rib or other roast that you'd want to cook to a perfect medium rare -- roasting from a "cold start" would make a difference in the tenderness. When a low and slow (covered) roast is prepared however, (especially something like brisket, pork shoulder or pot roast that is generously marbled), it needs to be cooked until the membranes break down and everything turns deliciously ooey-gooey. With a covered pot, enough liquid so that it is not roasting "dry," and an oven temp 325F or lower, even a frozen roast of this kind could be successfully prepared by just roasting a little longer -- until the meat is fork tender.
You can't really compensate for cold meat by raising the oven temperature during cooking. (I have Alton Brown to thank for this discovery.) Doing so just means that the outside will be burned while the center part is raw or very rare.
Instead, double bag your roast or big old hunk of meat with zip seal Glad bags or whatever brand you prefer, and put the meat in a large quantity of warm to hot water in a larger container or your sink. Sqeeze out the excess air from your bags (before sealing) to prevent the meat from floating. You do not want the water so hot that it cooks the meat, but that is unlikely unless you put in boiling water. The meat will warm up pretty fast because the water surrounds the meat in the plastic bags and convection currents will do the rest. If the water seems to be cooling down, dump it or drain it out and add some more hot water.
Obviously, if your meat is floating, put something heavy on top of it, like a frying pan or a half hotel pan with canned food on top of it. That'll sink the meat and keep it in contact with the water! I can't predict how long this will take, but it is pretty quick, surprisingly. I hope that this helps.