I really couldn't say. The publisher of a book is something I don't usually notice when I'm browsing in a store, and even less when I'm buying from Amazon or B&N.com.
My book buying choices tend to be driven by author familiarity, recommendations from people with similar taste, whether the plot synopsis on the back or inside flap grab me, and whether or not the first page or so reads well. Also (since I've been on these writing sites), I may buy a book from one of the authors I've "met" if they sounds like something that might interest me.
A perusal of my shelves (which are a mix of recent purchases and books I've had for decades) shows that I have a lot of SFF books from DAW and TOR, some from Orbit and Bantam/Spectra. There are ones from a smattering of other publishers as well, and since I've been buying more books online lately (and e-books too), smaller publishers are better represented among my recent purchases than among the books that have been in my library for years. I didn't see anything by Roc, but I didn't look at every book in my collection.
Not sure if the weighting towards Daw and Tor are more about the sheer number of books by prominent SFF authors they've put out over the years versus their tendency to publish books that are "more to my taste" than other SFF imprints.