Is a wife considered disobedient (nashiz) if she goes to the rooftop of her house for less than fifteen minutes due to fatigue and distress, and what is the ruling on that?

If your husband forbids you from going onto the roof, you are obligated to obey him. In that case, your going out would be considered an act of defiance (nushooz), unless you are compelled to do so. However, if he does not forbid you, your going out is not considered an act of defiance. The foundation of the marital relationship is affection, mercy, understanding, and overlooking minor faults.