Earplugs. The cheapest and easiest form of snoring 'treatment'. Suggest your roommate not sleep on her back and try breatherite strips. Finally, strongly recommend a visit to a board-certified sleep medicine or ENT specialist to evaluate the snoring -- it could save her life if she suffers from obstructive sleep apnea!
Goodluck. The easiest thing to do is wear earplugs. It just might work. If that doesnt work, ask your roommate to sleep on their side. Also if you notice your roommate stops breathing in between snoring, you should alert them as they might sleep apnea. In that case, they should see a sleep physician who could help and in turn help you.