There are two main disadvantages to mixing on headphones:
1) Imaging and sense of acoustic space dramatically suffer, but electronic music rarely relies on these
2) Mix translation suffers unless you're careful to compensate (this is a big one)
If I was in your space with all the problems you mentioned, I would mix on headphones. Fortunately, good sounding headphones are way cheaper than good sounding speakers and room treatment. Way cheaper. The two main types:
- Open-back headphones are best for detail and accuracy. But they don't isolate much noise. These are preferred if your roommate is gone a lot or is very quiet. Most of the best headphones in the world are open-back. I really like my AKG k702.
- Closed-back headphones offer isolation from sounds around you, but they generally are not as clear or detailed as open-backed headphones. Closed-back headphones are essential for recording vocals and any instrument requiring a microphone. (And useful if your roommate watches TV or does noisy stuff while you mix.) I really like my Sennheiser HD280 Pro.
As I mentioned, translation suffers when you mix on headphones. But you can work around this:
- Listen to your near-finished songs on lots and lots of stereos: car stereo, living room stereo, Bluetooth speaker, earbuds, your friend's fancy stereo, etc. If it sounds amazing on your headphones and sucks on everything else, your mix isn't translating. You'll need to listen, take notes of problems you hear, then fix them in your session. Repeat the process until your mixes sound as good as they can be expected to sound from all stereos, not just your headphones.
- SonarWorks has headphone calibration software that you load into your DAW for $100. If you buy headphones on their list (and you probably should), your frequency response will be a lot closer to what it needs to be, requiring less testing on other stereos. Consider this tool or an alternative.