Cervelo's 2012 squoval bikes, the R5ca, R5, R3 all have the same head tube length for their respective size bike frame. The RS has a longer head tube compared to the frame sizes of the other three.

The Roubaix SL-3 head tube is slightly longer than the Cervelo RS. Even on on both of these going back to the 2008 models, they have not changed. That means the head tube length of the 2012 Roubaix has not changed since 2008. Same goes for Cervelo RS.