There are two kinds of “bolts with bearings”. One type is where a bolt goes through plastic, then has a bearing, and then has a lock nut. The bottom three bearing of a roller is one example. You just tighten these ones such that there are not lose. You cannot adjust anything else with these.
The second type has plastic on both sides of the bearing. The top two bearings of the roller is an example, and there are more on the center assembly. With these ones, when you tighten the nut, you also squeeze the plastic from both sides. Typically, when you tighten this kind of bolt, the other two bearings will be squeezed together a bit more, so that all three bearings will touch the tube.