I personally do not rough up the surface but I do always run my piece over a jointer just before glue up to remove any oils that build up from sitting around. TBB1 explains this by saying take a piece of wood and put a drop of water on it, now take a plane, jointer or a knife and remove the top section of the wood and place another drop on this section. The area where wood was not removed, the water will puddle up (due to the oil). The area where wood was removed the water will dissolve. You want glue to soak into both pieces to insure a good bond.