Well, in that case I must come to RES-can's defense. In AE, at least in my experience, a double room is not the same as a room with only one double bed.
Nowadays, the normal, default hotel or motel room in the US or Canada has two double beds. You usually don't even have to ask for it, you just get it. Most of us don't think about what it's called, but if we had to give it a name, we would probably call it a double room. If you want to be doubly sure, you can just say, That's two double beds, right?
If you want anything different, you have to ask if they have any singles (one person) or suites (family or a small group). You can ask about a twin room, but you probably won't find one except perhaps in a B&B (bed-and-breakfast).
twin bed - Einzelbett (ein Mensch)
double bed - Doppelbett (zwei Menschen)
twin room - Zweibettzimmer (zwei Einzelbetten)
single room - Doppelbettzimmer (ein Doppelbett)
double room - Standardzimmer (zwei Doppelbetten)
There is also a difference between a double bed (generally speaking, any bed for two people) and the mattress size officially called double or full.
twin - Einzelbett
full aka double - enges Doppelbett
queen - Standarddoppelbett
king - breites Doppelbett
Whether for rooms or beds, the size we think of as normal is usually just smaller in Europe than in America. There are several threads in the archive, but since the links still aren't working, the Wiki table really is a good overview of the exact mattress measurements. One more try with the link in angle brackets: