It is different for everyone apparently. But I just read that more than 50% of Crohn's patients also have celiac disease (both are autoimmune), so I highly suggest a gluten free diet and possibly milk free to see if it helps eliminate most of your problems. My brother-in-law has Crohn's and most of his relief came from the gluten free diet. You can look it up online. You can't cheat - must be 100% gluten free including vitamins and medications. Hope this helps!
From what I have heard from those with Crohn's, there is no one diet for everyone. Some find they can not handle roughage. Others seem to find that diary doesn't work very well. It may be a trial-and-error thing you have to work with to see what your system can handle. You might want to try a board that deals strictly with those who have Crohn's and can give you a number of first-hand experiences.