Roll program

In the case of many NASA crewed launches, the commander reports the roll to the mission control center which is then acknowledged by the capsule communicator.

[2] The Saturn V's roll program was initiated shortly after launch and was handled by the first stage.

It was open-loop: the commands were pre-programmed to occur at a specific time after lift-off, and no closed loop control was used.

This made the program simpler to design at the expense of not being able to correct for unforeseen conditions such as high winds.

So the incentive to roll was initially for the payload increase by minimizing drag losses and moment balancing losses by keeping the main engine thrust vectors more parallel to the SRBs.