Well I was with you until you said you were happy with any room as thats exactly what you got. Its your error. Its not their problem you are living in a box room or that your mum and dad got divorced.
That said if you are unhappy, then you should address the issue now. because you have let it go, then that means someone else has to move into the room you dont like so you are happy and they become unhappy. You should have known the rooms were different and there would be an issue between who got which room.
Option 1 complain to them and force one of them to take the small room you dont wnat.- wont happen without some major resentment which will posion the atmosphere of the house and your friendship.
Option 2 leave and find somewhere else, but you will need to find another person to take your room and get LL's consent.
Option 3 Have a house meeting and ask them to reprice the rooms, so the larger ones pay mopre and the person who gets the smaller room pays less. You keep lowering the price of the room until someone takes it. The bidders agree to pay the balance of the rent between them. This would be an equitable solution. You could do this by auctioning the rooms off between you.
Unless they are very good friends, then I doubt they will listen to you, whcih might mean option 2 is your only choice. Option 1 is a bad deal, but option 3 has potential if they were willing to listen which i dont expect them to be. Its a situation you got yourself into and should have chosen a house with rooms all of a similar size or addressed the issue before the rooms were chosen. You could have drawn lost for instance.