How does treasure rolls work?

I rolled up a little over 3000 gp worth of goods (Mostly from the gems.) when I was rolling for a group of 6 bandits and that seemed like a lot to me so I thought I would ask here and make sure I'm doing it right. They are listed as J, N, Q type loot and I rolled this for each bandit is this how I'm supposed to do it or should I just roll once for the whole group?