Tom -
 
If the only thing you're doing is replacing syslog with syslog-ng, then the only thing you'll have to change is the restart line in /etc/logrotate.d/syslog:
 
    postrotate  
      /etc/init.d/syslog-ng restart
 
Of course, if that's all you're doing - why bother? :)
 
But basically, they're the same.  I'm using syslog-ng on our RHEL5 servers to split the logs up better, so that, for instance, they're not all going to daemon.log.  snmp to snmp.log, iptables stuff to various firewall-*.log, etc.  So mine looks like this:
 
/var/log/servername.log
/var/log/firewall*.log
/var/log/snmp.log
/var/log/auth.log
/var/log/daemon.log
/var/log/kern.log
/var/log/lpr.log  
/var/log/mail.log
/var/log/boot.log {
    missingok
    sharedscripts
    compress
    postrotate
      /etc/init.d/syslog-ng restart
    endscript
}


From: syslog-ng-bounces@lists.balabit.hu [mailto:syslog-ng-bounces@lists.balabit.hu] On Behalf Of Tom Simons
Sent: Monday, February 15, 2010 6:51 PM
To: syslog-ng@lists.balabit.hu
Subject: [syslog-ng] syslog-ng with logrotate

We're replacing sysklogd on our RHEL4 & 5 servers with syslog-ng-premium-edition 3.0.4-1. 

Has anyone configured logrotate to work with syslog-ng?  Can we just build /etc/logrotate.d/syslog-ng from 
/etc/logrotate.d/syslog?