Grainy Mustard Rotisserie Prime Rib Roast

In bowl, whisk grainy mustard, rosemary, Dijon mustard, Worcestershire sauce, oil and pepper. Transfer half to large bowl; add roast to large bowl, turning to coat. (Make-ahead: Cover and refrigerate roast and remaining mustard mixture separately for up to 12 hours.)

Follow manufacturer's instructions for using rotisserie. Or for 3-burner barbecue, remove grill racks. Place drip pan along centre of barbecue. Pour water into pan to depth of 1 inch (2.5 cm). Heat barbecue to medium-high. Turn centre burner off.

Clamp end of roast with rotisserie fork. Insert spit through fork and centre of meat. Clamp other end of roast with rotisserie fork. Position on barbecue with roast centred over drip pan. Start rotisserie motor. Close lid and grill over medium heat for 30 minutes.

Brush with half of the reserved mustard mixture; grill for 30 minutes. Brush with remaining mustard mixture. Grill until meat thermometer inserted in centre registers 140u00b0F (60u00b0C) for medium-rare or 155u00b0F (68u00b0C) for medium, about 30 minutes.

Transfer roast to cutting board; pull out forks and spit. Tent with foil and let stand for 20 minutes before slicing thinly.

Horseradish Aioli: Meanwhile, in bowl, stir mayonnaise, sour cream, horseradish and Worcestershire sauce. (Make-ahead: Cover and refrigerate for up to 8 hours.) Serve with roast.

Additional information : Tip: Top sirloin premium rotisserie roast, inside round rotisserie roast and eye of round oven roast of the same weight are all succulent cooked on the rotisserie following this recipe. Times may vary slightly depending on thickness.