Originally Posted by
gsteinb
A trainer is unquestionably superior to my mind. I can hit my target warm up zones without concern for traffic lights other cyclists. I don't need to worry about getting too far away from the start, or flatting.
+1
The only advantage to rolling around is to talk/plan/whatever with teammates.
Best combo is warmup with rollers/trainer, then go find team mates and roll around for a few minutes.