i've used the White Labs Kolsch yeast too, and fermented at about the same temp as rhoobarb. but, i conditioned mine in my keg fridge for 3 weeks at about 38-40 degrees. that strain of yeast is the exact opposite of a California Steam/San Fransisco yeast strain. Lager strains at ale temps, as opposed to ale strain at lager temps. the WL Kolsch will be okay at room temp, just fruitier and not as clean finishing. mine came out good/.