Am I to assume that syslogd also executes /etc/logrotate.conf? If so where is this documented? So far I've read what gets done but not how it gets done.
I don't think execute is the proper term here...but I think we're on the same page anyway. *.conf files are usually "read in" by their respective programs, and are I guess executed within the program, but it isn't a true execution. They generally direct their owner on how to execute.
As far as the automatic execution goes... You might want to check the /etc/cron.* directories (if you have them) for something related to logrotate. There are usually /etc/cron.d, /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly, and /etc/cron.monthly. As you might guess, hourly goes off every hour, daily every day, etc, so long as it's setup in the crontab (usually is by default). Anyway, I'd be willing to bet that within one of those (probably daily), you'll find something related to logrotate.