Heat oven to 350°F. Combine seasoning ingredients; press evenly onto all surfaces of beef roast.
Place roast, fat side up, in shallow roasting pan. Insert ovenproof meat thermometer so tip is centered in thickest part of beef, not resting in fat or touching bone. Do not add water or cover. Roast in 350°F oven 2-1/4 to 2-1/2 hours for medium rare; 2-1/2 to 3 hours for medium doneness.
Prepare Roasted Fennel, if desired.
Meanwhile, prepare Horseradish Sauce. Beat cream in medium bowl just until soft peaks form; do not overbeat. Add fennel bulb, horseradish, fennel fronds and salt; mix well. Cover and refrigerate until ready to serve.
Remove roast when meat thermometer registers 135°F for medium rare; 145°F for medium. Transfer roast to carving board; tent loosely with aluminum foil. Let stand 15 to 20 minutes. (Temperature will continue to rise about 10°-15°F to reach 145°F for medium rare; 160°F for medium.)
Carve roast into slices; season with salt, as desired. Serve with horseradish sauce and roasted fennel, if desired.
Roasted Fennel: Trim off and discard fronds and stems from 4 large fresh fennel bulbs (about 3-1/2 pounds) to within 1 inch of bulbs. Cut each bulb lengthwise into quarters. Place on metal baking sheet. Drizzle with 2 tablespoons olive oil; toss gently to coat, keeping fennel pieces intact. Season with 1/2 teaspoon salt; arrange cut side down. About 2 hours before roast is done, place fennel in lower third of oven. Roast for 1-3/4 to 2 hours or until tender and lightly browned, turning and rearranging once.
Nutrition information per serving: 387 Calories; 171 kcal Calories from fat; 19 g Total Fat; 8 g Saturated Fat; 7 g Monounsaturated Fat; 134 mg Cholesterol; 143 mg Sodium; 3 g Total Carbohydrate; 0.5 g Dietary Fiber; 48 g Protein; 3.2 mg Iron; 13.6 mg Niacin; 1 mg Vitamin B6; 2.7 mcg Vitamin B12; 8.9 mg Zinc; 55 mcg Selenium;