Talking the push from above comment i can add that most tube rollers forget, that current manufacturers create their gear with modern tubes for sound and characteristics in mind. Also they do not assume or expect that everybody will do tube rolling. They go with what is available at the time of production. On the other hand we are not certain that a NOS tube would bring vast improvement, many times it can be the opposite. This means proceed with caution, money spent elsewhere in the system can sometimes yield better results.
But you would not know if not trying and that is a part of the game.