Thanks to WattsupWatts for the suggestion!

Mick
The distraction. Basically the guy who distracts the tellers by flirting with them and shit.

Keith
He would be shit faced and waving a gun around like a fool saying "look! We're not going to hurt anybody. We just want the money."

Brian
He would be a nervous wreck and the look out.

Charlie
He would be one of the people shoving money in a bag.

Bill
Would be the get away driver because he was so good at driving Brian's van.