This is an announcement for the paper "Rosenthal operator spaces" by Marius Junge, Niels Jorgen Nielsen and Timur Oikhberg. Abstract: In 1969 Lindenstrauss and Rosenthal showed that if a Banach space is isomorphic to a complemented subspace of an L_p-space, then it is either a script L_p-space or isomorphic to a Hilbert space. This is the motivation of this paper where we study non--Hilbertian complemented operator subspaces of non commutative L_p-spaces and show that this class is much richer than in the commutative case. We investigate the local properties of some new classes of operator spaces for every $2<p< \infty$ which can be considered as operator space analogues of the Rosenthal sequence spaces from Banach space theory, constructed in 1970. Under the usual conditions on the defining sequence sigma we prove that most of these spaces are operator script L_p-spaces, not completely isomorphic to previously known such spaces. However it turns out that some column and row versions of our spaces are not operator script L_p-spaces and have a rather complicated local structure which implies that the Lindenstrauss--Rosenthal alternative does not carry over to the non-commutative case. Archive classification: Functional Analysis Mathematics Subject Classification: 46B20;46L07;46L52 The source file(s), njnpart1new11.tex: 38162 bytes, njnpart2new11.tex: 48325 bytes, refnew11.tex: 4840 bytes, rosmatrixnew11.tex: 10401 bytes, uncomp2.tex: 6528 bytes, x3njn1111.tex: 5668 bytes, is(are) stored in gzipped form as 0701480.tar.gz with size 33kb. The corresponding postcript file has gzipped size 176kb. Submitted from: njn@imada.sdu.dk The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/math.FA/0701480 or http://arXiv.org/abs/math.FA/0701480 or by email in unzipped form by transmitting an empty message with subject line uget 0701480 or in gzipped form by using subject line get 0701480 to: math@arXiv.org.