When I brought my Roam in to the bike shop, he said he could almost guarantee that the bottom bracket needs to be tightened. He said they check the torque on the crank arms during assembly (which are already installed), but this isn't the first bike where he's had to pull the crank arms back off and put a turn or so into the bottom bracket. He said that it's usually the drive side that's a bit loose, but it was the non-drive side on my bike which needed a tighten. It's all better now. I should have thought to check that when I had the crank arms off.
Bike shop was great, though. I brought it in around 5pm, he said he needed to build a new Sedona for a lady, and then he'd check mine and get it out. He called by 6:30 and I was there before they closed at 7 to pick it back up. Great customer service (and, now, a quiet bike!).