If you go to registration>registration list, you will see a list of all those registered for the league as well as the team they are on. If you click on sorting options and add team ascending to the sorting order, you will be able to see who is not listed on a team yet.

An alternative method would be to navigate to setup>teams>draft tool and go through each level to see who hasn’t been assigned to a team yet, they will be listed at the bottom.