ROXA: a new multi-frequency selected large sample of blazars with SDSS and 2dF optical spectroscopy

Blazars are a small fraction of the overall AGN population but contribute in a fundamental way to the extragalactic cosmic backgrounds in the hard X-ray and γ-ray bands and are the largest contaminant of CMB fluctuation maps. So far the number of known blazars is of the order of several hundreds, but the forthcoming AGILE, GLAST and Planck space observatories will detect a very large number of new objects of this type. We present the Radio - Optical - X-ray catalog (ROXA), a list of 816 objects among which are 510 confirmed blazars. This is useful for the planning of future identification work using SWIFT, AGILE, GLAST and Planck data.