Here's something I found, which might seem counterintuitive, and with which you may or may not agree: When standing, you might use upper body strength to try to maintain the bike more upright, or let the bike rock much more freely minimizing any input at the bars. In the first case, the only way to maintain balance when shifting your weight left and right on the pedals is to weave the bike left and right a small amount, and you can see this as moving steering left and right and can feel it as you alternately pull on the left and then the right of the bars. In the latter case, allowing the bike to rock freely, the angle of rock itself maintains balance as you shift your weight back and forth and no steering input is required (though you are flopping the bike back and forth). For me the bike tracks straighter and is easier to ride on the rollers allowing it to rock. If you try this, experiment on the road first and I'd be curious to hear what you find.