here's the appropriate section of my nsd.tcl on one of my boxes that
rolls the server logs. Let me know if you figure out which settings
you need to roll the server logs.
ns_section "ns/parameters"
ns_param home $homedir
ns_param debug false
ns_param MailHost mail.vorteon.com
ns_param ServerLog /var/log/nsd/server-${server}.log
ns_param LogRoll on
ns_param LogMaxBackup 5
ns_param KeepAliveTimeout 0
ns_param MaxKeepAlive 0
ns_param PidFile /var/run/nsd/nspid.${server}