When people need a list of root certificates, they often turn to Mozilla's. However, Mozilla doesn't produce a nice list of PEM encoded certificates. Rather, they keep them in a form which is convenient for NSS to build from: https://mxr.mozilla.org/mozilla/source/security/nss/lib/ckfw/builtins/certdata.txt?raw=1.
Several people have written quick scripts to try and convert this into PEM format, but they often miss something critical: some certificates are explicitly distrusted. These include the DigiNotar certificates and the misissued COMODO certificates. If you don't parse the trust records from the NSS data file, then you end up trusting these too! There's at least one, major example of this that I know of.
(Even with a correct root file, unless you do hard fail revocation checking you're still vulnerable to the misissued COMODO certificates.)
So, at the prodding of Denton Gentry, I've open-sourced a tool for converting NSS's file to PEM format: extract-nss-root-certs. (At the time of writing it requires a 6g built from the weekly or current tree (hg -r weekly), not the release tree. A few of the APIs have changed since the last Go release was done. This will be resolved when Go 1.0 is released.)