Preheat oven to 425°. Sprinkle tenderloin with salt and pepper. Cook tenderloin in 2 Tbsp. hot oil in a large skillet over medium-high heat 5 minutes on each side or until browned. Let cool 5 minutes.
Meanwhile, arrange pancetta slices in 2 rows on a large piece of wax paper, overlapping to form a rectangle the same length and width of tenderloin.
Sprinkle garlic and rosemary over tenderloin. Place tenderloin on edge of 1 long side of pancetta. Tightly roll up tenderloin with pancetta, using wax paper as a guide. Discard wax paper. Tie tenderloin with kitchen string, securing at 1-inch intervals. Transfer to an aluminum foil-lined baking sheet, and brush with remaining 1 Tbsp. oil.
Bake at 425° for 30 minutes or until pancetta is crispy and a meat thermometer inserted into center of tenderloin registers 120° (rare). Let stand 10 minutes. Discard kitchen string before slicing. Serve with Whipped Horseradish Cream.
Note: For medium-rare, cook tenderloin to 135°, or to 150° for medium.