Fortuna = Tyche (Τυχη, which is luck in Greek, as fortuna is luck in Latin).

While I have not really considered whether to make a distinguish between the Roman and Greek gods, as of right now I will say that they are the same in this universe.  Of course, the Roman versions have some nuances that are not present in their Greek counterparts (and vice versa).  However, I think that having both Roman [b]and[/b] Greek pantheons could easily get confusing and I feel they would be too similar.