1. By relics I assume you mean unique items. Who knows whether it's intentional, or whether the code that generates "random" required items is truly random.
I'm not sure about how the list of items is generated, but it
seems that the sages (with their list of required items) move around the map. I think that's why we occasionally come across the same list (of course, I have no proof)
2. Since the list of items for making uniques and scrolls is random (maybe), all items have potential uses. I've never seen a bedroll required by a sage or wizard though, so if you have a tent, then the bedroll can probably go.
I've never seen a sage ask for a 'usable item' either, but you can't use a tent in the city so if your advy wants to rest on the cheap it's best to keep the bedroll! It's good to keep the "junk" item as well (why does everyone want to throw it away?), let them pile up and sell a bunch for toll money if you ever get stuck :p
