Take pork shoulder out of the fridge about 1 hour before roasting and let rest on kitchen counter.
Preheat oven to 450 F (220 C).
Make little cuts into the pork's skin being careful not to cut the meat, only the skin, about 1" (2.5 cm) apart. (This will allow the pork shoulder to absorb its seasoning better).
Generously salt and pepper the piece of meet using your fingers to rub salt into the cuts in pork skin.
Apply aji amarillo with your hands, too. Quantity will depend on guests, if they can eat and like eating spicy. In my case I only use 1 Tbsp because small children are eating from it, if it were only for my husband and me I probably would have used 4 Tbsp. If you can't find ají leave it out completely.
Place pork with skin side up in a large roasting pan or a deep baking sheet.
Add cut-up vegetables and whole garlic cloves in their skin around the pork, salt and pepper vegetables and then pour a couple dollops of vegetable oil over the vegetables and mix well.
Roast uncovered in very hot oven for about 30 minutes.
Take out from oven to cover with aluminum foil making sure it holds tight to the boarders of the roasting pan or baking sheet (wear gloves to prevent burnings).
Reduce oven's temperature to 350 F (180 C)!! and roast for 2 hours.
Take out of the oven and let rest for about 10-15 minutes before cutting into the meat.