New technologies and approaches lead to the Internet of Things (IoT) paradigm. Such a paradigm enables the engineering of more autonomous and smarter software systems solutions. Due to its multidisciplinary nature, it involves several knowledge areas such as software and connectivity that should be combined coherently and uniformly. It should comprise different voices and expertise to deal with IoT in a multi-faceted way. In this context, what to consider while specifying, designing, and implementing IoT software systems? This work raises this discussion by defining a roadmap about what should be considered for engineering IoT software respecting all their facets. Such a roadmap is defined based on evidence acquired at the technical literature combined with a qualitative study