I was watching a live chess game. The opening was a Rossolimo, which I always thought was harmless. I was watching white slowly build up his centre and by move 13 he had achieved this. To my surprise, black resigned on move 19! To my eye, at move 13, black was okay, but clearly white disagreed! Even now, after reviwing the game several times, I still don't sense the danger on move 13 (like I would do with other tactics/positional ideas that I am familiar with). I found this game to be really instructive regarding the power of the mobile centre!

Thanks for your input pfren.

Is the Rossolimo as good as the mainline Sicilians for white? It seems more logical to me: instead of "sacrificing" the central d pawn (for black's inferior c pawn) in order to gain activity and a lead in development, white uses black's lack of development (1.c5) to slowly build the classical centre (pawns on e4 and d4). Should I make this my main weapon instead?

If black was worse by move 13, how should he have played the position beforehand?