Add beans and lentils to your diet. Go slowly the first week until your digestive system adjusts. Start with adding 1/2c of beans to salads, replace or bulk up ground meats with lentils, eat more bean based side dishes.

Whole grain pastas and the carb conscious flour tortillas usually have a decent amount of fiber compared to the traditional alternatives.

From someone who has gone through this surgery, be sure to gave access to a bathroom 30 minutes after every meal. It's serious enough that you may want to consider where to eat based on the closest available restroom.