Conceptual modelling (CM) involves analysts working with domain experts to create a representation of the domain called a conceptual model. We address two issues of CM research. The first deals with the meaning that conceptual models convey. We propose guidelines for how analysts can reflect the concept of a “role” in a conceptual model using the extended entity relationship (EER) method. Roles are important in organizations, but analysts have little guidance about how to model them. The second issue focuses on the effect of prior domain familiarity of the users on the understanding of conceptual models. We conducted a laboratory study to determine how domain familiarity affects users’ understanding of conceptual models that represent roles. Our results indicate that conceptual models can be developed to show roles more clearly but that the benefit of doing so depends on model readers’ familiarity with the modeled domain. In particular, our guidelines will be most useful when users have moderate knowledge of the domain shown in the model. When users are very familiar with the domain, the guidelines do not seem to have much benefit. However, when users have very little knowledge of the domain, the guidelines do help to a certain extent.