In the interest of helping those I care about (and those I don't even know) to learn from my mistakes, please take into consideration the following advice:
Unless you desire a late, late, LATE dinner, please note that the cooking instructions on the roast (or turkey, or whatever form of meat...) usually give the cooking time in minutes PER POUND, not cooking time for the whole thing. Thus, you must mutliply the cooking time stated by the weight of said cut of meat.
ps- I'll have you all know that the dinner turned out fabulously and that my family greatly enjoyed it. So what if they were too hungry to taste the food?! It was ONLY two hours later than planned. Shut up. You know you've all done something just as dumb, if not more so. Fine. Laugh all you want. I'm leaving.