There is nothing to simulate or model, you need an actual speaker cabinet in an actual room, and ideally that room needs to be the typical bedroom or den type of environment hobbyist guitarist tend to play in. You'll notice no one wants the sound of an amp in the basement or amp in the garage, because those acoustics are awful.
The 'problem' isn't the source, its the acoustics of the room.
Think of it this way, you can record a performance in a great concert hall and use a bunch of mics, mix it all together and its a very accurate capture of the sound, but then when you go back and play it on a speaker/monitor, its the sound of the venue and performance coming from a point source, which will have some room interactions in itself, but it is not going to achieve the same acoustics as actually being in that concert hall, and all those instruments, from lots of different seats, as you heard it from a given "sweet spot" in the concert hall.
I don't know why people have such a tough time grasping the concept really.....
Take an amp, ideally an open back combo, play it in a given room. That is the amp in room sound. Now take that same amp and go play it in your bathroom. Sounds different, its still "amp in room" but its going to be far more reverberate as the acoustics of the room have changed.
Unless your listening to a speaker in a true anechoic chamber, your ALWAYS going to hear the direct sound of the speaker/source, AND the reverberations of the room. Big hard surface room, your going to hear the direct than a lot of reverberation. Small carpeted room, you'll hear the direct and a lot less reverberation.
Its the exact same thing for vocalist. People like how they sound singing in the shower due to the acoustics. Singers however never seem to suggest they can't perform or record without their "voice in room" sounds, but guitarist, some at least, are apparently so used to the familiarity of how they've dialed in their tone at home, that they apparently can't otherwise play without that sound. Stick a mic in front of their cab live or for recording ? Suddenly they've lost the inspiration and can't play their best, so they say.
"Needing" amp in room is essentially the same as only being able to sing when your in the shower.