30 minutes prior to cooking, remove the beef from the fridge to come to room temperature. Preheat the oven too 500 degrees. Line a small baking sheet with foil.
Pat the beef dry with paper towels. Brush with one tablespoon olive oil. In a small bowl mix 2 teaspoons salt, the dried rosemary, onion powder, sugar, thyme and black pepper together. Sprinkle all over the beef on all sides using your hands to press it on to the surface.
Place in the oven and roast for 15 minutes until it's beginning to get crusty and brown. Reduce the heat to 350 degrees and cook another 10-15 minutes until a meat thermometer reaches 125 degrees (for medium rare). Pull the beef out from the oven and let it rest for at least 25 minutes.
While the beef rests, make the cream cheese and horseradish sauce. Add the softened cream cheese, scallion, basil, parsley, 2 minced garlic cloves, 1/4 tsp salt and 1/8 tsp pepper to a small bowl, mix to combine. Season to taste with salt and pepper. Set aside.
Add the sour cream, horseradish, 1/2 tsp salt, and 1/4 teaspoon black pepper to a small bowl. Mix to combine. Set aside.
When the beef has cooled, pour any juice that’s accumulated on the pan into a little bowl. Use a VERY sharp chef's or carving knife to slice the beef into desired thickness. For French Dip Sliders, I like to slice the meat as paper thin as possible.
To assemble. Spray a large baking sheet with non-stick cooking spray. Line the bottom of each roll on the baking sheet. Spread a little bit of cream cheese on the bottom of each roll. Top with a few slices of beef. Sprinkle with salt and pepper. Cover with a top roll.
Place in sliders the oven and bake for 5-10 minutes until the cream cheese is melty, the beef is warm and the top roll is slightly toasted.
When the sandwiches come out of the oven, top with horseradish sauce.
While the sandwiches warm in the oven, make the au jus. Heat 1 tsp olive oil in a very small saucepan over a medium heat. Add 1 clove of garlic. When the garlic has softened, add the reserved juice from the beef and the beef broth. Simmer for 2-3 minutes. Season to taste with salt and pepper.
When the sandwiches come out of the oven, top with horseradish sauce. Serve with jus.