Dissolve steak seasoning in balsamic vinegar, then stir in olive oil. Place pork into a resealable plastic bag and pour marinade overtop. Squeeze out air and seal bag; marinate 2 hours to overnight.
Preheat oven to 350 degrees F (175 degrees C).
Place pork into a glass baking dish along with marinade. Bake in preheated oven, basting occasionally until the pork reaches an internal temperature of 145 degrees F (65 degrees C), about 1 hour. Let the roast rest for 10 minutes before slicing and serving.