Additional information is now being revealed in this live stream with Seagull
The point is, everyone is going to need to be willing to switch even within their role to best suit the team. You should ask of the other roles to consider changing heroes if the team has a particular strategy in mind.
People like to zero in certain roles and demand that they swap to play around them, but really the entire team needs to come up with and agree on a composition that works.
They can’t do it because it would speak ill of one of their pros.
Role Select is looking pretty good so far.