I figure most nanotechnology will work at room temperature and pressure.

This sounds correct to me. My current mental model is that low temperatures could be essential for general-purpose assembly and/or repair, but most of the products created (particularly the diamondoid ones) would function at higher temperatures.

Lower temperatures allow for advantages like superconductivity and higher CPU speeds, and vacuum allows for super-insulation and frictionlessness. So there will probably be cases where these conditions are desirable for efficiency's sake even if not absolutely required.