Wow! What a fantastic bunch of posts! There are some really good opinions in this thread. Thanks, guys, for taking the time to share your opinions and experiences.
For me, the secret is simple: Coffee grounds. I brew a pot of good coffee made with fresh ground coffee (not Starbucks or whatever.) I go the local coffee roaster and buy a good, quality dark roast coffee. I grind it myself and brew it. I make several diagonal scores into the top of the roast with a sharp knife, about an inch apart. Next, I apply some beef base paste all over the rib and put a tablespoon or so in the base of the roasting pan. Then, I take the freshly brewed grounds and sprinkle them generously over the meat making sure to put some in the base of the roaster with the beef paste. I season with fresh ground pepper.
In the base of the roasting pan, I add water, onions and one clove of crushed garlic. I never let the roast come in contact with the water nor do I cover the roast. I roast it @ 400'F for the first 20 minutes to get that nice crust and then low and slow at 225 - 250 until the center is 120'F. I choose no more than 120'F in the center because when the meat rests, the internal temperature will continue to rise as much as 10 degrees, perhaps a little more, which means the cooking process is still active. If the center is just south of medium rare when it comes out of the oven, by the time it is done resting, the center will be in that sweet zone just above medium rare.
But, for me, the secret to that "restaurant flavor" is the combination of coffee grounds and beef base paste.