Radio Objects with Continuous Optical Spectra, (abbr. ROCOS, also referred to as ROCOSes) is a group of about 80 astrophysical objects characterized by optical spectra anomalously devoid of emission or absorption features, which makes it impossible to determine their distances and locations in relation to our galaxy. They are considered to be a subclass of blazars, and are similar in their spectral characteristics to DC-dwarfs and single stellar-mass black holes.