BatmanNews picked up on BatmanOnFilm editing their story removing Black Mask as a possible role for Joesph. So currently it's up in the air who he is actually playing.
Previously Gary Oldman confirmed another unnamed villain would also be added. It could be nothing but combined with the debunk helps fuel previous rumors that had Joesph was playing Black Mask. The Gotham villain has been a fan favorite since the film was first announced. Considering Roman Sionis is a reality based villain and is well known/liked it's still possible. To be honest Black Mask is a strong villain as he focused his threats on Bruce Wayne not Batman and is an enemy of Catwoman. I also wouldn't be shocked to see Nolan develop a hybrid villain combining Alberto Falcone (Holiday Killer) and Roman Sionis (Black Mask) into one character.