Picture a traditional, small, square or cube-shaped room. This one is made completely of concrete or cinder blocks and has no windows.
Student or Learner
Two guys were imprisoned in a windowless cement block room.
What is a "block room"?
So the room is made of blocks and the cement is put everywhere between the blocks to make them keep together?
Is this what is meant by cement block room?
The blocks are made out of cement. They are cement blocks.
The room is made up of cement blocks.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.