Heat oven to 325° F (165° C)
Remove roast from package; pat dry with paper towels. Leave string netting on roast.
In a small bowl, mix together the basil, oregano, garlic powder, onion powder, salt, and pepper. Stir in the olive oil and make a paste.
Rub spice mix over the entire roast and place on a roasting rack in a roasting pan.
Place slices of butter on top of roast.
Bake, uncovered for 1 ¾ to 2 hours, or until a meat thermometer inserted in center of roast reaches 175 degrees F.
Cover roast with foil and let stand at least 10 minutes before removing string netting and carving.
