I thought you could make a basket or something out of willow roots. If they take up space you'd love to have free, I'd say drop it. If you got enough bank space I'd say keep them, you never know what they will be used for in the future. Jagex said the same about bird eggs (still no good use for them but that doesn't matter) a mod said you should keep hold to the things that are availible for every player, but not (yet) usefull. :)