Well, you can show up with zero knowledge of ballooning, and the pilot will be grateful for your help. Ballooning is hands-on, blue-collar flying; there is a fair bit of manual labor involved.

At the other end of the spectrum, experienced crew might be charged with pretty much the entire operation of the balloon until it leaves the ground, and as soon as it touches down again, as well as driving/navigating the chase vehicle, landowner relations, weather observation. They can also participate (under pilot or repairman supervision) in inspections, maintenance, minor and major repairs, and all sorts of other ancillary tasks.