Radio-loud active galaxies in the northern ROSAT All-Sky Survey IV. Properties of sources stronger than 100 mJy at 5 GHz

We present multi-frequency radio data for 741 extragalactic sources with a 5 GHz integrated flux density of > 100 mJy. These sources have been selecte d from a cross-correlation of an early ROSAT All-Sky Survey source list wit h a list of compact radio sources of the 5 GHz Green Bank northern sky surv ey (RGB sample). The majority of Sources were quasi-simultaneously observed with the Effelsberg 100-m telescope at 11 cm, 6 cm, and 2.8 cm. We have de termined the spectrum, size and linear polarization properties of these sou rces. We compare the radio data with ROSAT measurements and optical data. W e find that the X-ray selected radio sources, when compared with unbiased r adio source samples, are on average slightly more compact, show a higher fr actional polarization, a higher absolute rotation measure (RM), and have fl atter spectra. Absolute RMs are larger for steep spectrum than for flat spe ctrum sources and for extended than for compact sources. The average redshi ft increases with the radio flux density, which indicates that the X-ray se lected radio sources have a larger fraction of beamed radio emission. All s ource characteristics of the sample are in accordance with present unificat ion schemes for AGN, where X-ray selected sources are preferable looked at face on.