A room temperature starter is fine- after all, you're growing yeast and not making beer. Since my lager starters are much larger than my ale starters, I always make it early (like a week before brewday), so that I can decant off the spent wort. I chill the starter about 4-5 days before brewday, as it takes longer for lager yeast to flocc out and then decant before pitching.
I like to pitch my yeast when the yeast is 46-48 degrees and the wort is 48 degrees, and then allow it to warm up to fermentation temperature (usually 50). That seems to make the yeast very happy!