Allow the roast to stand at room temperature for 30 to 40 minutes before grilling.
Prepare the grill for indirect cooking over medium heat (350° to 375°F).
In a food processor finely mince the garlic, rosemary, basil, salt, and pepper. Add the mustard and oil and process to form a paste. Smear the paste all over the top and sides of the roast.
Brush the cooking grates clean. Grill the roast, bone side down, over indirect medium heat, with the lid closed, until the internal temperature reaches 120° to 125°F for medium rare, 1½ to 2 hours. Transfer the roast to a cutting board and remove the bones. Loosely cover the roast with foil and let rest for 20 to 30 minutes. The internal temperature will rise about 10°F during this time.
While the roast rests, make the dressing. Place the cream and garlic in a medium saucepan. Bring the cream to a boil over medium-high heat, and then lower the heat to a simmer. Cook until the cream coats the back of a spoon, 5 to 10 minutes. Remove the pan from the heat. Add the cheese, stirring to help it blend into the cream. Season with pepper.
Carve the roast into ½-inch-thick slices. Serve warm with the dressing.