> Is there a method to dump just the roles from a database, or otherwise > select them, so I can build a script to reload the roles? Otherwise, I > guess I'll just read the tables for each database and build the > security script from that.
Roles are not per-database; they are global objects. You can get a dump of all the roles with pg_dumpall -g.
If you really need to filter out roles per database, my best suggestion is to filter a global role dump them with the pg_shdepend catalog for each database.