The ROCO family of multidomain proteins extends across the eukaryotes, and has been implicated in numerous cellular processes. Following the description of mutations causing PD (Parkinson's disease) in a human representative of the ROCO family, LRRK2 (leucine-rich repeat kinase 2), a great deal of research has been carried out into these proteins. This review examines the published data regarding the roles the ROCO proteins are thought to play in cell processes, and how the structure and domain organization of these proteins relates to their function.