1. What triggers would I have to use to make interceptors roam a map?
2. Would I need hyper triggers?
3. Anything else on the topic of Junkyard Interceptor triggers would be much appreciated.
All you need is simply the 'Junkyard' AI script to make them roam around. Hyper triggers aren't really necessary (unless you want fast preserved junkyard AI script). I think, however, when an interceptor roams nearby an uninvincible enemy unit, that particular interceptor will fly back to the carrier it came from.
What you need to do is have a whole bunch of carriers off in the corner with a high health enemy beside them. Fill the carriers up to their hangar limit.
Then the carriers will attack, and interceptors will come out.
Use the move unit trigger to move the interceptors to another location on the map where you execute the junkyard AI script.
The interceptors will fly back to their carrier if you do not use the junkyard ai. By moving the carrier around it is possible to make interceptor designs, like Bolt_Head did.