Even if the unthinkable happens and we lose to UM, I can't see the Rose Bowl taking a 5 loss Northwestern over OSU.

There's only really four scenarios here.

OSU beats UM...makes playoffs...

OSU beats UM...doesn't make playoffs.....Rose Bowl

UM beats OSU, but loses to Northwestern....OSU ends up somewhere else.

UM beats OSU, beats Northwestern...OSU Rose Bowl.