Cooking a pork roast on a rotisserie grill set for direct or indirect low heat will take up to four hours for an average 5-to 6-pound roast. The finished internal temperature of the roast should be 145 F, when measured from the thickest portion of the roast.
Insert the thermometer so that it does not hit the rotisserie rods to get an accurate reading. When using a rotisserie oven, the cooking time depends on the oven model. Some ovens cook much quicker, requiring a cooking time of 20 minutes per pound, while other ovens require up to 50 minutes per pound. After cooking, on the grill or in an oven, the roast should be covered and allowed to rest for up to 15 minutes.