Preheat oven to 350 degrees F. Slice French bread loaf down the middle length-wise. Slice prepared Italian sausage links into small discs, approximately ¼ inch in thickness. Pour spaghetti sauce into a bowl and mix in sliced Italian sausage.
Open sliced French bread loaf and place onto a large baking sheet. Scoop Italian sausage and spaghetti sauce mixture onto the bread evenly. Add a single layer of sliced pepper jack cheese on both sides of the open French Bread on top of sauce and sausage mixture. Finish by sprinkling oregano and parsley over the cheese.
Bake for about 15 to 20 minutes, until cheese is melted, and bread has a hardened crust. Remove from the oven and close the sandwich, then cut into individual sub sandwiches.