This is also a question we are facing. We have a simple rectangular body defining our building. The selection of roof and floor tilt angles does not seem intuitive, and we can't find any explanation of these parameters in documentation. When we set the 'roof tilt angle' to zero, ARCHSIM seems to incorporate the roof surface of our zone as part of the facade (which does also include the body's four vertical walls correctly. To get our simulation to work, we have to rely on the default ARCHSIM values of 45 deg. for roof tilt angle and 135 degrees for external floor tilt angle, but we are not sure why.
It would seem these two parameters are also relatively new as they did not seem to exist in the version of ARCHSIM used for Solemma's video tutorials.
I can confirm this too with our work on similar models.
It seems that, provided you don't set any of the tilt angle parameters to 'zero', then they generally have no effect on E+ outputs.
The tilt angles in Archsim help the program to auto-identify which surface should be given the roof or slab constructions that you specified. The default is everything that has a tilt larger than 45deg will be recognized as facade. If the tilt is flatter then it will become a roof or slab.
Below you see two zones with different roof tilt angles. The settings are at their 45deg default. If the roof becomes too steep then it is recognized as facade.