End game or Main game?

Rooks are much more important in the endgame, not so much in the beginning.
They prefer open files and ranks, which are at low supply in the middlegame.
Rooks are much more important in the endgame, not so much in the beginning.
They prefer open files and ranks, which are at low supply in the middlegame.
Are rooks main offensive pieces or end game bruiser's? What do you think?