Once K began to initiate motion to kick, I would not grant R's time-out request in most instances, particularly if it is the head coach. While the rules state time out can be called during a dead ball period, it must be legally granted. To be legally granted, an official must be able to acknowledge that time out has been called. If K is initiating a free kick play, the officials' attention should be upon their area of repsonsibility.
Unless the R player was directly in your sight and you heard the time out request made, I think the play must go on at that point.
Similar to a wing official- the ball may be dead but if the snap is imminent, I'm not taking my eyes off the LOS to verify if it's the HC calling time-out.