Contextual information plays an important role in hiding technological complexities from a user's point of view in ubiquitous and pervasive environments. In terms of access control, contextual information can be used to minimize the set up and access control complexities and at the same time to allow users to gain access to resources pervasively without difficulties. RBAC has been used and adopted widely in facilitating an access control mechanism. A variation of RBAC is dynamic role assignment in which users are assigned roles based on their situations. This paper uses semantic contexts in order to determine appropriate roles assignment for an incident management system.