No, in order to stop protesters from blocking traffic, then that is all the police need to do. The protestors can always protest in a park or literally anywhere other than in the middle of roads.
In a just society, some group's right to protest does not take priority over everyone else's right to travel and use roads. Roads do not belong to activists, and no activist group has a right to shut down public roads without arranging this with police ahead of time so that appropriate detours can be made for normal traffic.