Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
The two things I can think of in this sort of case is, to check whether
A. the headphone jack has a jack in it, and
B. whether the MIDI OUT is enabled, which may cut off sound from the speakers.
After that, it would probably need repairing. If you let me know your local zip code, I can give you listings for all local Roland Authorized repair facilities near you.