This study characterized required skills and competences for data specialist roles by analysing job advertisements for data scientists and other related professionals. It was performed using a content analysis technique named centring resonance analysis (CRA). With the support of this technique, demanded skills were grouped into categories that allow a better understanding of each role as well as differences and similarities among roles were observed and analysed. This study also summarized our findings in an orientation framework to classify six data specialists' roles according to business and technical skills as well as to experience and educational demands. Professional experience seems, in general, to be more valued than academic background. This work sheds light on better differentiating job roles related to data science, which could guide companies that recruit such specialists by better defining job requirements. For universities, these findings support the development of new analytics and data science programs.