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I analyze unpublished or partially published archival ROSAT data of the rhoOphiuchi dark cloud. This set of seven overlapping ROSAT HRI pointings,composed of eight ~one-hour exposures, detects mainly the X-ray brightest TTauri stars of this star-forming region. Only two HRI sources are new X-raysources, and their optical counterparts are proposed as new Weak T Tauri starcandidates. Meanwhile the ROSAT HRI caught during just one exposure a weakX-ray source (maximum likelihood=10; SNR=4.1\sigma for Gaussian statistics)among a group of three embedded young stellar objects including two Class Iprotostars. Previous ROSAT PSPC, ASCA GIS observations, and as I argue here oneEinstein IPC observation, have already detected an X-ray source in this area,but this higher angular resolution data show clearly that X-rays are emitted bythe Class I protostar YLW16A. This is the second Class I protostar detected bythe ROSAT HRI in this dark cloud. The determination of the intrinsic X-rayluminosity of this event, L_X[0.1-2.4 keV]=(9.4-450)*1E30 erg/s, criticallydepends on the source absorption estimate. Improvements will be obtained onlyby the direct determination of this parameter from fitting of Chandra andXMM-Newton spectra.Comment: 4 pages, 2 figures, 2 tables. Accepted for publication in A&

ROSAT-HRI detection of the Class I protostar YLW16A in the $\mathsf{\rho}$ Ophiuchi dark cloud