But to be fair, my drum room is in my basement, so it has cement floors (which do not transfer vibrations well), and I keep most of my drum kits about 30 feet away from them or so.
It doesn't seem to upset them. Maybe if it was wooden floors (that transfer vibrations better), but really they only seem to be a little bit more alert when bands come over to rehearse (the bass guitar is usually the culprit). When I'm just practicing on my own they don't seem to notice at all.
Then again, there are other factors involved. For one, I'm a classically trained professional musician, so I don't play super loud. Loud playing is much more common amongst newer players. That seems to be my biggest complaint with teaching percussion instruments. Students seem to think louder is better. I guess they don't realize that any venue worth playing will have enough wattage to push your sound to all corners of the hall without having to wail.
I would just see how the tortoises react and then try different things. If they stop eating or show any other signs of stress, you can try to keep the vibrations to a minimal (muffling the bass drum and raising cages up off the ground). Make sure your roommate isn't playing too loud either (because that can also be harmful to your body if done incorrectly).
Oh, and by the way, egg crates won't sound proof a room. Sound proofing a room costs thousands and thousands of dollars. All foam and egg crates do is make the room sound more dead within the room.
Good luck.