There is currently no way of restoring users and roles to new databases with mongorestore. --nsFrom and --nsTo don't affect user restore.

Related: https://jira.mongodb.org/browse/TOOLS-104

The situation with --db with --restoreDbUsersAndRoles is a bit more complicated now that --nsInclude and the related options have been added. --db is now only meant to be used to describe which database a single bson file should be restored into. So --restoreDbUsersAndRoles really shouldn't require it at all anymore. We need to rationalize exactly what behavior we expect and then implement it.