The most robust way I can think of is to build a middleware service using our API and then providing your own filter. On the Auth0 side you will have to pick the method that suits best for your use case (depends on the number of roles, users and users per role):
1 - /api/v2/roles/{id}/users: query users by role (with pagination) > parse response to filter by name/email.
2 - /api/v2/users: query users using a querystring (‘q’ parameter) to narrow results down by name/email, then perform a second call to get corresponding roles.
Store the results in a temporary object / DB and access it via your own client/GUI.
A second method that I can think of (but I haven’t tested) is to add your user’s roles as metadata. You can then use metadata to query the users as explained here. This would allow you to use my method 2 above but with only one call per role (or less)
If you’d like to request the addition of a name / email or query filter on the Role API, I would suggest you doing it here.