Up until DMS a crew of rounded sets is a lot easier than giving everyone roles.
There are 13 buffs to carry (if you count both Sweetheart and Fleet Feet). So giving everyone in the crew two buffs works. Everyone having a heal or two like wish or bandage, meat depending on the area is a nice to have. As for attacks I've found a decent 1-1-1 build works. One range, one melee, one aoe. Of course a ring like slash can pull double duty as melee and aoe but I tend to prefer:
Hot Foot/Shuriken, Hack/Mantis, Fire Rain/Slash, Bandage/Free, Buff 1, Buff 2, Meat, Wish
Free meaning whatever I prefer in the situation be it another heal, a passive, or another attack.
Buff wise I tend to pair them when assigning like this, but feel free to mix and match to your preferences:
Div, Fleet/Sweetheart
Halo, Sphere
Ghost, Keen
Rock, Dense
Coyote, Teflon
Iron, Pot