From my understanding, the whole point of the root / trusted store (in a device, in a computer, on a server...) is that "the trust starts here". In other words, hacking, etc. aside, in theory all certificates in the trusted store don't need to be -- and really can't be -- "verified" per se; they are trusted implicitly simply by virtue of the fact that they reside in the trusted store.
So here is my question: do these certificates even need to be signed (from a security standpoint, not from a perspective of software implementations of certificate chain verification)? I guess more specifically, my question is this: does the digital signature on a certificate in the trusted store provide an added security benefit?
The only reason I could imagine these certificates need signatures is simply to make trust / verification easier, i.e. elimiate special cases in verification software -- all certificates must be signed, even if the signature of the certificate at the start of the chain is essentially meaningless.