I had a very positive experience w/ my roommates at college, and with my roommates since, and w/ college in general. I think good communication and planning is key. Some specific tips:
(1) Let the roommate know up front what to expect. Supply them w/ the key info, including the fact that having CF is not a death sentence, so that they don't look it up from a biased source (i.e. crazy people on the internet).
(2) Discuss w/ your roommate about your treatment routine and what that will entail. One roommate I had couldn't study that well when my neb was going b/c of the noise...we simply mandated that certain times of the day I was free to do my nebs, and if he wanted to study, he could try to, but my nebs took priority. But, understand that playing loud music would have done the same thing, so it was more just roommates getting along than CF.
(3) Discuss w/ your roommate the importance of keeping your personal info (i.e. having CF) private...you should be able to tell people that you have CF if/when you want to, and they need to respect that.
(4) Be prepared for questions from roommates/new acquaintances/friends/friends of friends/hookups/etc about why you have nebs and pills and a cough. I often found that telling people "I have this lung thing...it's kind of like asthma," while technically not true, was enough for most people to understand, and to not be afraid of me coughing.
(5) Investigate campus health services beforehand, and note if there is a doc w/ CF training in town. If it's a smaller college, then you may be the first CFer to go to that campus health. A planned visit to meet a doc at the campus health service over this summer (maybe during orientation) to discuss your health needs might be a good idea. Getting a doc that will communciate with the CF doc that takes care of you now would be ideal.
(6) Have a discussion w/ your CF nutritionist about college food. Often, dining hall food is loaded w/ fat, which can be a problem for CF pancreas. Having a plan about which items are likely to be easier on your GI system will be good...I had success w/ waffles/cereal/fruit for breakfast, sandwiches or a single slice of pizza for lunch, and watching the pasta (it's loaded w/ oil so it won't stick together).
(7) Talk to campus academic services beforehand about an emergency plan in case you need to go into hospital. Better to have one hammered out early than to be making one while calling the dean on your way to the hospital.
(8) See if you can make your roommate help you w/ your stuff, but don't overburden them...they shouldn't have to feel like your caretaker. At the same time, don't resent them if they are trying to help you...it's easy to roll your eyes at a parent when they remind you to do some nebs, but a roommate who reminds you doesn't have to...they're probably just trying to help.
Feel free to PM me if you have any other questions. Cheers!