That's how I do it. I have an extra corny that doesn't fit into my kegarator so I have a beer in waiting that goes into the extra keg that I force carbonate at room temp and then store until it's that beer's turn in the kegarator.
I force carbonate by turning the gas up to around (on average) 20-25 psi (adjustments are made for the right beer style) and then shacking the keg back and forth for 8-10 minutes. After that, back down to the homebrewery where it waits and the injected CO2 has a nice long time to dissolve into the beer. Works out pretty good actually because as soon as I kill one keg another is ready to go, no waiting a few days for it to get carbonated.
Having said this, I know Ashton Lewis or Mr. Wizard in BYO says he doesn't like force carbonating at all but he did not explain why. Also, when the beer is colder than room temp it is better able to absorb more gas quicker. But, if your situation is like mine then that doesn't really matter since the extra keg is waiting for other kids to be finished anyway