Originally Posted by forsooth
Is there a risk?
As pointed out by others, wait a month or so after the procedure has been published. By then it will have been thoroughly tested by many users and easy to use step-by-step instructions are available. In a worst case scenario it is possible to brick a device, but that is not irreversible, either. There will also be instructions on how to get it going again and return it to ex-factory state (if you can't find those, don't ever attempt to modify/hack a device). I find how-to-videos are the best, you see the instructions, you see it being done, and you see what happens on the device.
Just rooting is usually extremely simple, flashing a custom ROM takes a little more but is hardly rocket science. If you have some old device you may try flashing that one first to become more comfortable. If it is an Android device you will also find instructions on XDA.