Preheat oven to 350 degrees F (175 degrees C).

With a kitchen towel or paper towels, pat dry the pot roast. Turn roast fat side up. With a paring knife, cut deep slits between each rib. Stuff each slit with spinach and dried pineapple. Wrap the roast with butchers' twine to hold the meat together.

In a large bowl, stir together rosemary, parsley, poultry seasoning, garlic, garlic powder, onion powder, salt, cracked pepper, butter, and 1 1/2 tablespoons oil. Rub half of the mixture over the roast and inside the slits.

Heat 1 1/2 tablespoons oil over high heat. Sear the roast, turning to brown on all sides, about 5 minutes.

Transfer roast to a roasting pan fat side up; scatter carrots, potatoes, and onion around the roast. Pour remaining rub mixture over vegetables.

Roast, uncovered, in a preheated oven for 2 1/2 hours, until the internal temperature of the roast reads 145 degrees F (63 degrees C). Remove roast, cover with an aluminum foil tent, and let rest 20 minutes to 1/2 hour to ensure moistness. Slice along each rib, and serve with pan gravy.