You can do this with Valkyrie Rockets and other Killstreaks as well. I had a Napalm Drop Menu Open and while everyone else is counting down you position your Napalm to wherever you want to drop it in. When there is about 3 seconds left on the countdown clock call in your Napalm and the enemy will spawn and about 1 second later having no time to move will get burned. I guess the same would Apply for Rolling Thunder, etc.