If you turn off your iPhone, you can't use it again without entering your password, and you would have to do that consciously. On the other hand, your phone could otherwise be unlocked with just your fingerprint.
I don't know the verbatim message, but it says something along the lines of "Passcode is required to enable Touch ID"
Edit: with Touch ID enabled, if you slide to the lock screen without touching the sensor, it says "iPhone requires your passcode after restarting" but the title says "Touch ID or Enter Passcode"