I thought it was, "row-sin-on-tay."
This is how I said it, but I guess it should be "ross" 
I believe it is Rah-Sin-In-Tey
Not too hard to pronounce, really.
Um... wow, I've been really off, I thought it was "Rok-in-Aunt" with aunt not said like ant but like Americans do with southern accents. I always thought it was a pun on astronauts or some kind of "naut" or maybe "Rock in on" or something like that.
Any ways hilarious, didn't even know there was a conspiracy theory with the MG dev team until now!
(ps. at first I didn't acknowledge the last "N" in Rocinante, and I thought it was "Rok-in-Ate")