We are not talking radioactive fission products after shutdown but in principle, the concept is similar. The amount heat stored in a roast is proportional to the roasting temperature and the roast’s size. This means the roast must be removed from the oven at an internal temperature lower than desired final temperature. The residual heat is at the surface and successively less toward the center. The roast’s initial center temperature when removed from the oven will go up as the roast rests. The blue arrows in the chart show the direction of residual heat as the roast rests, while the moisture flow in the roast is just opposite as the roast’s protein molecules relax. Typically, resting times for a large roast is 20 minutes or more while a smaller roast maybe 10 to 15 minutes.
Looking at the figure again, the bands of color also represent a gradient of doness. For roasts roasted at high temperature, the outer rings may be well done, while successive inner layers are increasingly rarer. The secret restaurants use to get prime rib almost uniformly rare inside-to-out is to roast the meat at a low oven setting. In my cookbook, we use 220 F. which results in this uniformity. The temperature rise after resting for a 15 pound roast is only 4 degrees.