The bottom half of the Teams Info tab contains the Team Roster. You can find a nameplate for each member of your team. 

Clicking on a player's nameplate will show you their Username, Role, Level, and total Gold Flags  collected. Clicking your own nameplate, you willl be able to change your username. This can be done at any time. 

Leaders also have the option when clicking a member's nameplate to change their role or expel them from the team.