FA-06 ROM

I don't think Roland have ever revealed the Supernatural ROM size, so you may be out of luck. But other than that i beleive it's the same basic ROM set from the JV- family, merged with a selection of the newer Jupiter Supernatural ROMS.

May i ask why you are asking?

Many of the newer tones are achieved using modelling combined with sample ROM.

There is a list of the core sample waveforms that you can use in your own tones, if that's of interest?
https://static.roland.com/assets/media/pdf/FA-06_07_08_SoundList_multi01_W.pdf

(page 40 onwards)

Usually the more rom the better the sounds. Usually as each new model comes out they increase it.
Workout I’m also assuming it sounds better than Juno do I didn’t like the sounds on it at all.
Thanks

From what I have read and heard, the FA series sounds are derived from the Integra-7. That doesn't help with the OP's question about ROM size, but should give an indication of the quality of the sounds, which is apparently the real concern.

Tony