Router OS support AES 128/256bit encryption?
Yes it does, link to Wireless manual: http://wiki.mikrotik.com/wiki/Manual:Interface/Wireless#WPA_properties
your link address say as below.
Statically configured WEP keys
Different algorithms require different length of keys:
40bit-wep - 10 hexadecimal digits (40 bits). If key is longer, only first 40 bits are used.
104bit-wep - 26 hexadecimal digits (104 bits). If key is longer, only first 104 bits are used.
tkip - At least 64 hexadecimal digits (256 bits).
aes-ccm - At least 32 hexadecimal digits (128 bits).
TKIP is 256bit, but AES is 128 bit,
Router OS AES 256bit support?
RouterOS supports the features required by 802.11i standard, which means AES128
TKIP uses different encryption method, so you can’t directly compare bits between AES and TKIP.