The Mayo Clinic has a great outline about diet and diverticulitis at the different stages of healing. I hope you find it helpfyl:
I have many diverticuli in the sigmoid colon and a rather large one on the right side at my cecum. I have had three episodes of diverticulitis. One more infection in the cecal diverticuli and the GI said I will have to have it taken out. I make very sure that I get enough fiber in my diet now. I use a supplement, Fibersure, when I cannot get it through food stuffs alone.