This paper proposes a roadmap to address present and future needs in space systems with RISC-V processors. RISC-V is an open and modular instruction set architecture, which is rapidly growing in popularity in terrestrial applications. To satisfy different applications with contrasting requirements in satellite data systems, four different types of processors are identified: 1) low-area/low-power microcontrollers, 2) on-board computers, 3) general-purpose processors for payloads, and 4) enhanced payload processors for artificial intelligence. Several solutions based on RISC-V are proposed for each of these types of processors and compared with proprietary commercial-off-the-shelf and space-grade solutions. An extensive analysis of the results available from literature is conducted to show that RISC-V has the potential to solve such a wide range of needs. This paper will also show the unprecedented number of open-source implementations and models that were developed in a relative short time on a single instruction set architecture. Future space systems could benefit from many of those developments, and this work identifies and highlights what is still missing to satisfy the specific needs of processors for space, especially in terms of fault tolerance and technology readiness level.