Preheat your oven to 450° F.
In a small bowl, combine the butter, oil, garlic, rosemary, salt and pepper, and mix until a paste forms.
Pat the pork roast with a paper towel to remove excess moisture and then rub ⅔ of the seasoning mixture onto the roast, covering the top and sides.
Place the roast in the bottom of a large roaster.
Place desired vegetables around the roast. Dab the remaining seasoning mixture over the vegetables.
Roast in the pre-heated oven for 15 minutes, then turn the oven temperature down to 300° F. Do not open the oven!
Let the roast continue to roast for another 20-25 minutes per pound of meat, around 100 minutes or until the internal temperature reaches 140° F when a meat thermometer is inserted into the middle.
Remove the roast from the oven and cover it with foil. Let it rest 10 minutes, then slice and serve.
