In this context, "rojak" is a combination of English and another language (probably Malay or Pilipino).  The word comes from Malay, but Pilipinos use it too.

The term can also mean anyone who is of mixed ethnicity.

If you've listened to Pilipinos speak among themselves, they often use a mixture of Pilipino (one of the two national languages), English (the second national language), and whatever their mother tongue happens to be (Chabucano, Ilocano, Tagalog, Visyan, Cebuano, etc.).