No.
At least if the person building the ROM knows what they are doing.
From the documents (my attention):
Each key comes in two files: a certificate that has the extension .x509.pem and a private key that has the extension .pk8. The private key must be kept secret and is required to sign the package. the key can itself be password protected. The certificate, in contrast, contains only the open half of the key, so this can be widely distributed. It is used to verify that the package has been signed with the corresponding private key.
If your device has an unlockable bootloader, you can create and run your own ROM using a pair of keys that you created yourself. Thus, you will have the private key of the platform for your system application.
source share