The drag attributable to sufficient roll spoiler to off-set crosswind effect during takeoff is negligible, and it is accounted for. The primary purpose of the use of all roll control during a cross-wind takeoff is to negate the assymetric lift effects caused by the crosswind, a reasonable lift differential, but only a small increase in drag.
The actual drag will only be of the order of a few hundred pounds, balanced against tens of thousands of pounds of thrust, it truly becomes negligible. From a performance aspect, it is a "nothing", or close to it.
What is of importance, as illustrated in Boeing manuals, is that these few hundred pounds of drag are assymetric, i.e. they are on one side only, and this CAN have a significant effect upon VMCG and VMCA. V1 often equals VMCG, and a significant directional control problem can be in the making if EXCESSIVE spoiler application has been applied at this point, and engine failure occurs.
Boeing's technique is to apply roll control (including spoiler) as required during the Takeoff roll, but with decreasing wheel angle as V1 is approached. Ideally, the wheel angle should not be beyond the point where spoiler activation commences - Nor should it be, at that higher speed, aileron alone should suffice.
Regards,
Old Smokey