Preheat oven to 425ºF.
Let the roast sit on the counter until it reaches room temperature, about 30 to 40 minutes.
Pat it dry with paper towel and season with salt, freshly ground black pepper and mustard; set aside.
Heat an ovenproof pan over medium-high and add olive oil. When it gets hot, sear roast on all sides and ends.
Lift the seared roast and place a wire rack underneath before placing the meat, fat side up.
Insert a probe and transfer to the preheated oven; cook for 20 minutes.
Reduce the heat to 325ºF and cook until the internal temperature reaches 140ºF (*see footnote).
While the roast is cooking, in a medium bowl combine herbs and garlic. Pour in grapeseed oil, stirring, until the herb mixture is moist.
When the roast internal temperature reaches 115ºF, remove from the oven and quickly spread the herb mixture on top, pressing down lightly. Return the roast to the oven to finish cooking.
When the internal temperature reaches 140ºF, remove the roast from the oven and place it on a carving board. Tent the roast with aluminum foil and let it rest for 20 to 30 minutes to allow the juices to redistribute before slicing.