The main source of your confusion stems from misinterpretation of the phrase "Tesla's solar roof" which is solar roofing material produced by Tesla for building

The main source of your confusion stems from misinterpretation of the phrase "Tesla's solar roof" which is solar roofing material produced by Tesla for buildings rather than a solar roof for a Tesla automobile. I'm a 'comments first' reader myself but TFAs are generally a must read for context and disambiguation before actually wading in.