You can do this with a simple defaults write too.

defaults write ~/Library/Preferences/ByHost/com.apple.screensaver.*.plist idleTime 600

this will set the idle time to 600 seconds. Another way is to capture the preference, package it with composer, deploy and run a Fix ByHost afterwards.

I'm doing what entholzner suggests (defaults write). Users, of course, can then change it themselves, though, unless you lock down the pref pane. In our environment this isn't a big deal as we set display sleep to get the behaviour we want from machines left unattended, but thought I'd chime in on what might be a potential limitation to the defaults write (or Composer capture) method(s).