Preheat the oven to 400 degrees F.
Cook half of the bacon until crisp in a large skillet. Remove and set aside. In the same skillet that you cooked the bacon in, add the butter, mushrooms and shallots and cook for about 2 minutes. Add the crawfish and parsley and saute until tender. Pour the mixture out onto a baking sheet and add the cream cheese and mix together.
Sprinkle the tenderloin with the olive oil, soy sauce, salt and pepper. Spoon the mushroom, bacon and crawfish mixture down the center of the tenderloin. Bring the two sides of the tenderloin up around the filling to meet. Use butcher string and tie around the roll at 2 inch intervals. Top with the remaining bacon.
Roast until a meat thermometer inserted into the center of the meat reads 125 degrees F, 30 to 35 minutes. Let stand for 5 minutes before slicing.