Do they actually call them that where you live? In which case feel free to count them. But where I live they're just part of "drawer sliders" or "drawer runners".
If they don't, and you're calling them wheels just because they happen to be a circular rotary component of something else, we're back to dissembling everything to count the circles again. That's the point, to draw a line before it gets silly. Otherwise my vehicle has probably thousands of wheels inside it.