Diverticulosis can be tricky subject because certain people respond differently to certain foods. The research says that seeds and nuts should be ok to use but some people report having problems with them. You know your body best and should be able to identify which foods bother you and eliminate those from your diet. If you have not figured out which specific foods bother you, I would suggest keeping a food and symptom diary.
This can help you assess what foods might be a potential problem for you and what foods to avoid. You should be ok with most foods in the NutriBullet as it breaks foods up to a liquid consistency. I would suggest avoiding strawberries, blackberries and raspberries. Blend your food well and experiment with only several foods at a time. Include foods like ginger, turmeric, cherries, dark leafy greens, green tea, blueberries, edamame, cacao... as these are all anti-inflammatory foods. If you know that any of these bother you, do not use.
Try sticking to a bland diet when you are recording your food symptoms and add foods in one at a time. This will help pinpoint which foods are bothersome.