I am sure Rodolphus and Tiberius will be friends of a sort. I see Rodolphus feeling bad that someone as interesting as Tiberius got placed in such an unfortunate house, and him mentioning it time and time again when they do talk. As I said before I am certain he would know Tiberius from the Knights of Walpugis, and deem him somewhat worthy based on that alone, especially if he is active in it.