The procedure is really easy; however scary. If you are novice user - do read!
0. The first step is to let you know that Flashing erases everything on your phone memory. DO A BACKUP OF YOUR PERSONAL DATA!
1. First of all you need drivers, so your computer can recognize your phone. Download and use always the latest drivers from the Motorola website: http://developer.motorola.com/docstools/USB_Drivers/Handset_USB_Driver/
You may need to register an account there, but no worries - it's painless piece of cake.
2. Critical step - charge your phone battery in FULL! I warn you very seriously about that!
3. Go to Settings > USB Settings of your Motorola ROKR E8 and put your phone to "Modem" mode.
4. Plug the Moto to the computer with regular USB cable. You will see several recognition messages in the taskbar. Wait until they are all gone with confirmation.
5. This may be a problem - you need the RSD Lite flashing software (version 3.8 or later). The later version - the better and safer. Where is the problem you may ask - the problem is that the software is copyrighted and not free. Google will be your best friend to find where you can obtain it: http://www.google.com/search?hl=en&q=RSD+Lite
6. Start RSD Lite. It must recognize your phone and show your phone info on the screen.
7. Did you downloaded the firmware yet? I guess you do. Unpack the firmware to your desktop. It will be a large (70MB+) single file with .SBF extension. Now in RSD Lite click on the "..." to browse and select that firmware.
8. When the flash file is highlighted and recognized press START.
9. Now just wait! RSD Lite will shut down your phone and will put it in bootloader mode. Then it will start to unpack the firmware into codegroups and then finally - start to flash them one by one. All you have to do during that process is to sit down, relax, do not start any programs on your computer, do not trip up the power cables and most important PRAY! Yes - pray to not have any electricity problems or computer crashes. The moment is really critical for your phone. It may continue around 10-15 minutes.
10. We hope that you are lucky - the phone should say "PASS" and eventually turn on. Disconnect it from the USB cable and use it. If it do not turn on (but show "pass", "finished" or "please manually power up the phone") then you have to turn it on. It's not a rare scenario that it won't turn on. Do not panic - remove the battery, insert it again and then power on. If your flash went OK then you are ready to go!