Yeah, I'd be doing some intervals of varying lengths at about 90% of my normal pace. Go ahead and burn a couple matches during warmup, but make sure you have 5 minutes of easy spinning before the start (to clear the lactic acid).
Lance's prologue warmup used to consist of 3x 5 minutes at 500w. Cut the duration in half and wattage down to 400 or so, and something like that should work for you.