In a mixing bowl, combine soy sauce, olive oil, minced garlic, brown sugar, and black pepper to make the marinade.
Place the pork roast in a large resealable plastic bag and pour the marinade over it. Seal the bag and refrigerate for at least 2 hours, preferably overnight.
Preheat your oven to 350°F (175°C).
Remove the pork roast from the marinade and place it in a roasting pan. Discard the marinade.
Roast the pork in the preheated oven for 90 minutes, or until the internal temperature reaches 145°F (63°C).
Let the pork roast rest for 10 minutes before slicing and serving.