There is some debate on the "best" way to start a lager but everyone I've talked to recomends a monster sized starter. A vial or smack pack just isn't enough yeast cells to do the job. I don't ever ferment my lagers at room temperature or even start them there although some brewers do. I'm not a big lager fan, but when I make them I really want the clean crisp flavor profile that the lager yeast provides and that only works if the fermentation is at lager temperatures.
What I do is make the starter and ferment at coolish room temperature and step it up a few times and then chill it and decant the spent wort (I don't want that spent wort in my lager after fermenting it at room temperature). It takes about a week to get a large amount of yeast. Then, when the yeast is at 45-48 degrees and my wort is at 50 degrees, I pitch the yeast into it. It seems like the cooler yeast and the slightly warmer wort get going quickly. After the primary is just about done, I do the diacetyl rest (if needed), then rack and secondary for a couple of weeks and then start dropping the temp for the lagering period.