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 at least 2 hours or overnight. The longer it marinates the better the flavor will infuse.
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 45-60 minutes. The marinade may start to smell like it's burning in the pan on the sides but the pork is not. Let the roast rest for 10 minutes before slicing and serving to let the juices settle.