The primary issue is the rescue media must (1) be able to boot, and (2) must be able to see your image file. Part (1) is easy because the imaging program can be installed on another PC after the fact and new rescue media created using a generic WinPE image (sometimes part and parcel with the program itself). Part (2) is a bit more iffy because if your image file is on your NAS then that rescue media must include the proper network driver for the hardware the media will boot from, which may be dfferent from the hardware on which the media is being created.
One way to work around this problem is to install the imaging program on the subject computer, then immediately use the create-rescue-media function to make an .iso file rather than physical media. Then at any point in the future another computer could use that .iso to create a USB stick when needed. (Of course, you'll want to do a trial run to make sure that .iso can successfully see your NAS.)
This solves the problem of having to carry around a janitor's keyring worth of USB sticks for every machine you support, since you can use a single USB stick and just reburn it with the .iso you happen to need at any given time.)
Another way is to restore the image to a target disk in another working computer. For instance, a bare metal disk can be attached as a secondary disk to another Windows or Linux machine on which the imaging program has also been installed, and the program can be run from there, pointed to the image on your NAS as the source, and pointed to the secondary disk as its target. Then the secondary disk can be moved back to its rightful computer and booted from there. That method can have some potential pitfalls, as I've noted in my video, but there are usually repair options if that should happen.