15 dried bay leaves, crumbled, plus whole leaves for garnish
1/3 cup coarsely chopped fresh sage leaves, plus whole leaves for garnish
1/2 cup extra-virgin olive oil
1/3 cup finely grated orange zest, (from 3 oranges)
Freshly ground pepper
1 (about 7 pounds) three-rib prime rib of beef, trimmed and frenched
3 pounds russet potatoes, peeled and halved lengthwise
Stir together bay leaves, sage, oil, 1 1/2 teaspoons salt, and the orange zest in a small bowl. Season with pepper. Rub herb mixture all over the roast. Refrigerate roast, covered, overnight.
Put potatoes into a large pot of water. Bring to a boil; add salt. Cook 5 minutes. Drain. Score lines lengthwise in potatoes using the tines of a fork.
Preheat oven to 450 degrees. Transfer roast, fat side up, to a metal roasting pan; let stand until it comes to room temperature, 30 minutes to 1 hour. Roast 15 minutes. Add potatoes; roast 15 minutes. Reduce temperature to 350 degrees. Roast, turning potatoes after 30 minutes, until an instant-read thermometer inserted into meat (away from bone) registers 115 degrees.for rare, about 1 hour.
Let stand 20 minutes (temperature should rise to 125 degrees., and slice. Garnish with bay leaves and sage.