Spec for the extreme roadblock:
Maybe like some said was a roadblock that both member have to do
OR
Maybe it's kind of like a U-Turn, in which after you open your clue and know what the task is, you can force one member of another team to complete that specific task. Exemple: If the task is very physical, a team got use the extreme roadblock on another and force the weaker member to do it. That would create trouble for teams that are not well balance.