Juice oranges and limes in a mixing bowl.
Add minced garlic, olive oil, and seasonings.
Whisk everything until fully combined.
Place pork in bowl or zip bag.
Pour marinade over pork generously.
Cover and refrigerate for at least 8 hours.
Preheat oven to 300°F before cooking.
Place pork in roasting pan.
Cover pan tightly with foil.
Roast pork for 3 to 4 hours.
Remove foil and roast 30 minutes more.
Check pork with thermometer (190°F tender).
Let pork rest 15 minutes before slicing.
Garnish with cilantro before serving hot.