Touchjudges do more than call touch or do conversions, it doesnt seem like it because everything else is done via radio communication now.
Offside is a team call, the touchjudge will tell the referee via the radio that player x is offside, it is then the referees decison whether to penalise or have a word on the run, its the same with forward passes and knock ons, the tj will call it to the ref through the radio but the referee might think from his angle that the play was ok and over rule him. Done that myself as an official and was proved right on tape.
On National League games and below (if radios aren't available / working), the TJ only signals an infringment (forward pass, knock on) if the referee gives him eye contact. The only time the flag is used nowadays is for touch / goal and foul play calls (and part of the signal for forward pass)
99 times out of a hundred when a fan calls "gerremonside" its about a player who isnt involved with play so therefore isnt offside, they are only offside if they interfere. It annoys me when I / or any other official try to get a player back and all we hear is "PUT YOUR FLAG UP THEN" I know where I'd like to shove it one day, but the feelings more than mutual
