Hello Nathan,
The Team Webmaster role does not allow for managing rosters. However, the Registrar role can be limited to a specific team if needed. So the person requesting the ability to add players to their roster would have both roles - "Team Webmaster" and "Team Registrar".
The limitation of the Team Registrar role is that they cannot add players or coaches to the master list - they can only assign players or coaches which already exist in the master list to their own team.
Hope that helps,
Shaun