I was running RFC with my level 15 shaman who is also a leatherworker, and a leatherworking recipe for crafting a leather foot item dropped. It wouldn't let me roll need because "your class may not roll need on this item". It didn't make much sense, as my class uses leather, and besides isn't it more of a profession-based thing to roll need on it? What if I'm making the armor for other characters?
Suggestion: allow sub-40 shamans and hunters to roll need on leather, and also lock need rolls for recipes based on whether you have the profession or not, and not based on whether or not you can use the produced item. If necessary, require players have the same profession level or one lower (for instance you must be at least artisan to roll on a master item) to prevent people cheesing on need rolls by swapping professions.
Report this in the bug tracker with exact details such as the recipe name in question. I don't think this is a bug with leather recipes and armour types in general, sounds more like a particular item bug... as for sub-40 shammys and hunters not being able to roll need on leather... is this actually the case for all leather drops? If so, this is hilarious xD
P.S. suggestion section here is not for bugs, if something is just wrong and not how it should be whatsoever, then report it in bug tracker and campaign for everyone you know/meet with similar issues to vote it up and make people more aware of bug tracker... even if it takes 6months-1year to get many things fixed... it's the only system we have, and it does work, just with extreme bias (no love for bgs or other pvp related things, or random things that 99.9% of the population would never notice, even if they are voted up hard) and sloth :/