400 motor parts

Ok I got some rockers, small block heads but no BB heads. I guess I’ll just wait and decide later what heads to get, do all CNC BB heads require offset rockers?
No. (And there are various offsets available). The bigger, more racy the head, the more likely to use offset rockers. Really has nothing to do with the cnc, more with how much the pushrods are moved over to straighten the shot of the intake port. (Kinda like tubing a small Mopar to widen the pushrod pinch).
Trick flows have special rockers from Harland Sharp, but I don't think they are offset, just a different reach from shaft to roller.