www.rotel.com has a link which shows the IR protocol, device and function numbers. It is NEC1, device 131.17 (0x83.0x11 in hexadecimal).
I'm familar with remotes made by Universal Electroncs. The UEI remotes known to handle the RSP-1066 (without buying a $29 computer interface cable) are:
OneForAll models--
URC-7555 (One for All 5 digital, 7556 shold also work)
URC-7940
URC-7950 (Comfort line 5)
URC-8350. (Use Setup code 30793)
Also the Pace DStv PVR URC-3989 will work.
Use setup code Audio 0793 for these execpt the 8350.
Nearly any OneForAll, some cable remotes, high end Vizio TV remotes, etc. can be made to work if you also buy the
computer interface cable.