Comment # 3 on bug 1212853 from Matt Weber

When you LUKS encrypt a standard artitions with a password, each partition that
is LUKS encrypted will require the user to decrypt it with the password that
was established during the LUKS setup.  So if you LUKS encrypt root, /home, and
[SWAP], you would need to type 3 passwords during boot.  The only exception
would be if @/home was a logical volume under root, in which case it would be
decrypted once root is decrypted.    

Once other note: 
Since [SWAP] is encrypted, you may have difficulty resuming from a Hibernate
sleep state if you ever put the system in Hibernate mode.  Personally I'm not
sure why anyone would do this because it's faster to boot the system from a
shutdown, so this is really just an FYI.