In small bowl, mix garlic, salt, pepper, rosemary and oil; rub mixture over beef.
Let stand at room temperature 30 minutes.
Place pan on lowest oven rack.
Heat oven to 450°F.
Insert ovenproof meat thermometer so tip is in thickest part of beef and does not touch bone.
Roast uncovered 45 minutes.
Reduce oven temperature to 350°F; roast 45 to 50 minutes longer or until desired doneness (140°F for medium-rare, 155°F for medium).
Cover loosely with foil; let stand 15 minutes.
In small bowl, mix sour cream, lemon juice and horseradish.
Carve beef; serve with horseradish sauce.
Notes / Tips / Wine Advice:
Festive Touch
The specialness of prime rib calls for equally special side dishes! Try Bacon-Thyme Duchess Potatoes (see recipe) and Holiday Romaine Salad (see recipe).
Kitchen Secrets
How do you accommodate guests with a range of preferences for doneness? Poll your guests, roasting the prime rib until the center is cooked to the preference for the least-done beef (such as rare or medium-rare). Serve the ends of the roast to those who like their beef the most done and the next slices (working in toward the center of the roast) to those who like their roast a little less done. Save the center for those who like their beef the least done.
