Duty Roulette should be an option in Duty Finder, at the top of your DF list. I'm not sure what level you are so maybe it isn't an option for you yet. It's just like queuing up for any other duty finder and will put you in any dungeon you've completed on random. Best results if you're a tank or healer.
Pink gear sets are better than plain pieces, and their stat spread is random and different for each pink piece of the same gear (usually). Green is the best you can get for that level and will complete a full green set. So a green weapon is better than a pink, while a pink is usually better than a normal. Sets can only be completed from the same dungeon (I think), and so you won't usually be able to complete a green set over a range of level 15, 17, 21 dungeons etc. Fr example, the Battlemage set (green) can only be completed and found in Brayflox, a level 32 dungeon.
When Need is available you should, more often than not, click it. Need means it is suitable to your current job, so you're gonna want it. If 2 people "Need" an item, they both roll for it and at the point it's luck for who gets it. If you have an item level 30 weapon and you have the option to Need a level 20 weapon, technically you can need it but you won't use it. However as it's suitable for your job, the option is given to you. Use your best judgement in these cases. Greed is used when you want the item and it's not for your current job. If nobody chooses to Need and 2 people choose to Greed, they then roll for the item. If 1 person chooses to Need and 2 choose to Greed, the person who Needs will get priority and win the item. If you want none of, just Pass
Hope that helps!
