Good day!
No, it is not possible. And we cannot say it is a limitation, it is reasonable.
In general, different accounts are given to different people, accounts which are used for different operations on managed devices or Agile Controller.
If a higher level account can change the roles of a lower account (or can change the roles of the same level), it will not be safe. All newly-created accounts are managed by default by the admin account, which is the safest.
Current rules:
1. All newly-created accounts cannot change each other's roles.
2. A newly-created account can decrease the amount of its own roles, but cannot add more. If the amount is decreased, it will not be able to add itself again - only the default admin account can add again.