I know how you feel. I felt that way too when I was first prescribed Rowasa. It really is not that bad, and it has saved me many times from going into an out of control flare. I always make myself a bed of towels in the bathroom so that I can stay there for awhile after I have admisiterd the Rowasa. Bring a book!!
Whether or not you are able to retain the medicine kind of depends on how bad your current flare is. The first time I used Rowasa I had trouble retaining it the first couple of nights. Other times it has been fine. I usually have my most trouble with "going" in the morning, so by evening I am usually okay. I think that your individual situation will determine how well you retain the meds.
I would take Rowasa over prednisone any day of the week!! If it works for you, it gives you relief without all of the awful side effects of steriods. Good luck!