SystemPanel strives to support as many devices and versions of Android as possible, including custom firmware/ROMs and rooted phones.
That said, a custom ROM generally does not receive as much development/quality control/testing by its developer(s) as does a factory ROM. You may find that some features of SystemPanel do not work with certain custom ROMs. This will occur most frequently with ROMs which are under heavy development, e.g., those with "beta" status. Issues are less likely to occur with popular, well-supported, well-tested ROMs. Issues are more likely to occur on ROMs which contain major upgrades past what a device manufacturer currently supports, e.g., a device whose current supported OS is Android 2.1 (Eclair) running a custom Android 2.2 (Froyo) ROM.
If you encounter an issue, please feel free to report it to NextApp by posting it on our forums at android.nextapp.com. We also recommend that you contact the custom ROM developer.