Rinse pork tenderloin under cool water, pat dry with paper towels, and place in a plastic storage bag or container.
Make marinade. Mix mustard, olive oil, garlic, thyme, rosemary, paprika, pepper and salt in a small bowl until well combined. Pour marinade over pork and ensure it is well coated.
Allow to marinate for at least 20 minutes or in the refrigerator up to 24 hours.
Preheat oven to 425 degrees. Place pork on a sheet pan lined with aluminum foil. Roast for 35 minutes until internal temperature reaches 145 degrees. Allow to rest for 10 minutes before slicing.
Serve with Horseradish Sauce: Combine sour cream, horseradish, lemon juice, vinegar, paprika and salt until well combined.