For now, we're able to have only 1 Owner for each license. But after your subscription, you can add Admins to your Team so they'll have similar permissions as the Owner.
One of the biggest differences between an Owner and a Team Admin is that only the Owner can manage billing information. But for the rest, admins can do it all like adding and removing people to the team, managing boards, etc.
If you want to know more about EasyRetro user roles click here.
If you want to know how to assign Admins to your Team click here.