Hi John
I can't think of a way to show which capability has precedence when a user has more than one role.
The precedence is calculated using numeric values assigned to each capabilty (inherit = 0, allow = 1, prevent = -1, prohibit = -1000) and multiplying by the context level - the lower context has higher value than lower. The capability with the highest value wins.
If there are problems with the precedence then overriding or assigning to a lower context should help the precedence of the capability.
Try and keep the assigning of multiple roles and overrides to a minimum as they are difficult to sort out .maybe consider creating a user with the separate admin role that people can login to rather than having users with multiple roles. Users who have a learner and an admin role in the same course will be able to change their own grades.
regards