Hi Nick,
You can't find anything about the ROM space in any of the documentation. I had to file a service request to find out about it.
But the ROM wasn't my original question in the service request. Notice that there are multiple part numbers for the DSP56371: DSPB56371, DSPC56371 and DSPD56371. I wanted to know the difference between them, and which one I should order.
I was told that I needed to order the "DSPB" variation, because it does not contain any ROM code. The other variations contain ROM code that requires a license. So that ROM space is reserved for Dolby, DTS or other proprietary audio algorithms that you might need and have a license for.
So for me, the ROM space isn't even there in the chips I use.