Blocking rules on roll-out passes
 

Quarterback rolls out to his right on a run-pass option. When exactly can the receivers downfield start blocking? What would the specific penalty call be in this situation?

I'm not sure you're asking the right question.

Downfield blockers can start and continue blocking whenever they feel like it. There would be no penalty for blocking...

... until the quarterback passed. If the "option" ended up being a pass, then ANY downfield blocking becomes offensive pass interference (retroactively if you will). There's no time limit. You simply can't block downfield on a play that ends up being a pass.

You can block if the pass is behind the LOS and the lineman are downfield. It depends on where the pass ends up.

Peace

We've had one of these in each of the last two games. Last night the coach for the offending team was yelling at the offending player before I even made the signal.

To put the restriction slightly differently:

Blocking downfield is legal unless it is OPI. Restrictions on A players begin at the snap and apply if a forward pass crosses the LOS.

Reminds me of a coach we had this season who asked "How come you wait throw the flag for an ineligible downfield until the quarterback throws the pass?"

I made the mistake of not holding my flag in that situation back in my early days... Had to then tell my white-hat that I had a flag for ineligible downfield on a QB scramble that gained 15 yards. (Yes, we picked up the flag).

I saw a crew enforce this penalty in a game this year. The coach had to correct them. They did realize their mistake, but unfortunately nobody knew where the run had ended. They had to guess and were off by 5 yards.

Had a JV game where the covered end went downfield. B coaches behind me were screaming at me to throw a flag. After scrambling around the QB finally threw to my side wideout. I threw my flag, told the R what I had and went back to pick up my flag. The coaches said it was about time I threw it. I told the it was not a foul until a forward pass was thrown. They laughed and said they would be quiet now!