Pre-heat the oven to 190 degs. Brush the beef generously with the horseradish and season well and place on a lined baking tray. Toss the cut vegetables with the oil, salt and rosemary and arrange in a single layer around the beef. Roast for 15-20 minutes or until the vegetables are tender and the beef cooked to your liking. Rest for 5 minutes before slicing the beef thinly. Combine the horseradish, sour cream, lemon juice & zest and season to taste.
Arrange the salad greens in a shallow serving bowl and top with the roasted vegetables and sliced beef. Drizzle over the horseradish cream.