On OS X, open the app Keychain Access and look at the System Roots keychain -- you can see all the root certs there.

For Windows: Have never done this myself, but the link mentions a tool called RCC that lists root certs and highlights potentially suspect ones I guess? No clue if this is legit, use at own risk: https://www.wilderssecurity.com/threads/rcc-check-your-syste...