Playing with Friends!

So recently, I've been playing normals with a bunch of friends, and we try to go as 5 as often as we can. However, we noticed something strange when we play together. We all pick fill and that's how we decide the roles, but no matter what, we always end up in the same roles. It doesn't matter who the captain is, it doesn't matter what order we get into the lobby, it doesn't even matter what day it is, we always get the same roles.