At the present time, if a coach or player has been assigned to a roster then they can not be removed from the master list. This is because the site archives previous seasons and preserves all team information for, at the present time, perpetuity.
Sometime in the near future we will need to have a conversation with associations about data retention and what a suitable / reasonable strategy would be for storing historical information, and what information should be preserved. For example, perhaps it's reasonable to store schedules forever but rosters / stats / news / photos etc could be auto-deleted after X number of years.