Decrypting an encrypted text out of order
$\operatorname{ROT}(n)$ is also known as the Caesar cipher.

$\operatorname{ROT}(n)$ can be thought of as a character based stream cipher. It works because addition - the encryption method used - is commutative. In other words

$\operatorname{ROT}(x, \operatorname{ROT}(y, m)) = \operatorname{ROT}(y, \operatorname{ROT}(x, m))$.



Another well known commutative function is $\operatorname{XOR}$. It is used by the one time pad, but - more practically - also for block ciphers in streaming mode.

So you can encrypt using AES in CTR mode using two different keys in any order and get the same ciphertext. And decryption will work in any order as well. 

Note that you should use an IV or nonce if you reuse the keys. Reusing a key stream generated from the key and IV breaks confidentiality. Together with $\operatorname{XOR}$ it breaks the scheme as you can XOR out the key stream.