Hey El, the main reason to have the cab in a separate room is to prevent/reduce spill from the backing track(s) into the guitar (or other) track. This is much more necessary when you use a sensitive condenser mic on the cab. With a 57 (which IIRC is what you generally use to mic your cab) you won't get as much spill as it's a dynamic quite directional stage mike designed to provide reasonable separation on stage etc. You could give it a try in the same room, make sure the mic is facing away from the monitors, the louder the monitors the more potential for spill (obviously) but given your not going for perfect "studio" separation it may well be adequate for what you want. Another option is to monitor with headphones (as you would for vocal overdubs etc.)
As Peter says, if you have the cab in a separate room and turn the monitor up loud enough, you'll get feedback. I hadn't thought of touching the monitor with the guitar, interesting idea.