The incubator and research projects sponsored by the Center for Research in Open Source Software (CROSS, cross.ucsc.edu) at UC Santa Cruz have been very effective at promoting the professional and technical development of research software engineers. Carlos Maltzahn founded CROSS in 2015 with a generous gift of $2,000,000 from UC Santa Cruz alumnus Dr. Sage Weil [6] and founding memberships of Toshiba America Electronic Components, SK Hynix Memory Solutions, and Micron Technology. Over the past five years, CROSS funding has enabled PhD students to not only create research software projects but also learn how to draw in new contributors and leverage established open source software communities. This position paper will present CROSS fellowships as case studies for how university-led open source projects can create a real-world, reproducible model for effectively training, funding and supporting research software engineers.