First and foremost you must be unlocked to flash any roms on your phone you can get the unlocker at this link
http://rhodiumw.htc-unlocks.com/hard-spl.php Unfortunatly Due to the new process unlocking is not available via the SD card so you will have to find a PC if you don't have access to one.
If you are going to flash any of Cmonex's special patched radios you will have to be sim unlocked you can do this
http://rhodiumw.htc-unlocks.com/ Again This has to be done with a computer.
now once you get that piece out of the way we can get to the fun part, flashing a new rom without the aid of a pc. Similar to the mogul days and touch pro days, I have found flashing new roms much more convenient from the SD card than from the PC that way I could let my phone download the rom and then flash to a new version while I am out and about. Another added benefit is to be able to keep multiple roms on your SD card so you can test one, but still keep your standby at hand and not be locked to your computer.
A pre-note to this process. Your SD card must be formatted fat-32 (not just fat) for this process to work. formatting your SD card will wipe out all information on it so remember to backup first!
This is actually a really simple process.
Step 1: find the rom/radio you wish to flash and download it
Step 2: extract the .nbh file out of said rom package (will usually be named RUU_SIGNED.nbh if the rom is packed in an exe use pocket rar to extract from your phone or 7zip/winrar from your pc)
Step 3: rename the .nbh file to RHODIMG.nbh
step 4: place rom on the root of your SD card (meaning not in any folders)
step 5: power down the device completely
step 6: hold volume down and power (sleep/wake button on the Verizon variant) till the screen boots into bootloader mode (red green blue screen)
step 7: when prompted press power to flash
step 8: wait for it to finnish, sometimes it will restart on its own, sometime you need to restart it yourself but make sure you wait for the flash successful screen.
That's all there is to it I will add to this as time goes on. Happy flashing!