You can either:
Use irotate.exe as pre and post commands in Maximus to rotate the desktop on the fly in conjunction with your current emulator, or
use MESS's NES emulation, which rotates as MAME does, if that's good enough for the games you want to run.
If you use irotate to rotate the desktop, keep in mind that your emulator could have trouble with full-screen modes if it assumes that the typical 3:4 modes will be available.