change the solar absorptance of roof outermost layer based on outdoor dry bulb temperature

edit

I don't believe you can add/edit EMS objects using the OpenStudio Application (or App), at least not without Measures. You can however with the OpenStudio CLI/SDK (which comes with the App). You'll need to setup an environment (ex. for Ruby bindings). There is a learning curve, yet it's worth the effort IMO. Once up and running, I suggest you start off modestly at first (baby steps), then move on to what you're after. The OpenStudio-resources simulation tests (e.g. EMS) are really great for beginners. You'll also find nice examples in the OpenStudio-EMS-Measures repo (namely this one ... not too far from what you're after). You can certainly actuate surface absorptances using EMS.