Can one room be both a bedroom and office?

Yes, with two-in-one furniture.

Two-in-one means one thing has two jobs.

Mika lives in a very small room.

Each morning, her bed is up on the wall.

A desk is ready in front.

She studies and drinks tea there.

But at night, something changes.

The desk stays flat.

She pulls the bed down.

Her study place becomes her sleep place.

Some wall beds work this way. (resourcefurniture.com)

So, one room can do two jobs.

Good furniture gives your space more life.