Edit role
From the "Roles" window, click on the card of the role you want to edit.
Make the changes you want and click "Update".
Permissions will automatically be updated for all collaborators who are assigned that role. Only the project owner can do this.
Remove role
From the "Roles" window, click on the three dots in the upper right corner of the card of the role you want to delete.
Select "Remove".
Confirm you want to delete the role by clicking "Delete".
Note that any collaborator assigned that role will still have the permissions given to them by the deleted role. Only the project owner can do this.