It would be handier if the disksizes are on the same row in the CSV.
Name,Datastore,DiskSize1,DiskSize2,DiskSize3
VM1,ds1,10,20,25
VM2,ds1,10,20,0
Then you could do
Import-CsvC:\list.csv-UseCulture|%{ New-VM-Name$_.Name-Datastore$_.Datastore-DiskGB$_.DiskSize1,$_.DiskSize2,$_.DiskSize3-GuestId"windows7Server64Guest"
}
If the DiskSize is 0, there will be no harddisk created