C. rosaceus is believed to feed mainly on seagrass detritus. In contrast, specimens from shallow turtle grass meadows in the Belize Barrier Reef have been found to forage primarily on calcareous Halimeda debris although seagrass debris is the most abundant POM source. The urchins selectively ingest large-sized Halimeda particles, probably due to their high organic content and dense microbial colonization. Due to its preference for large particles C. rosaceus plays an important role in bioerosion.