$server = get-viserver -server <server> -user <user> -password <pwd>
Set-VM -Snapshot (Get-Snapshot -Name <Snp Name> -VM (Get-VM -Name <VM Name>)) -VM (Get-VM -Name <VM Name>) -Confirm:$false
Variant on the above to get you used to the pipeline:
$vmname = "foo"
$snapname = "weekly revert snapshot"
$vm = get-vm $vmname
$vm | set-vm -snapshot ( $vm | get-snapshot $snapname ) -confirm:$false
Hal Rottenberg
Co-Host, PowerScripting Podcast (http://powerscripting.net)