Didn't you contradict yourself about the roast cooking time? Is it 20, 25, 30?

The longer you roast per pound, the greater the degree of doneness. A 20 minute per pound roast will be on the rare side; 30 minutes will probably be well done. Two caveats: Unlike, say, a stew meat with high collagen, which will become more tender with longer cooking times, a roast such as this will become dried out and chewier. Also, just because you set your oven to 325°, for example, it doesn't mean your actual oven temperature is that. Get an oven thermometer, set the oven at the desired temperature, and see what the "real" temperature is. Then, adjust the setting on the dial until the interior oven temperature is exactly the one you want. Remember that setting and use it.