Here are the recommendations that I follow. They were given  to me by a bariatric program that is a Center of Excellence in Los Angeles, California:

Roux-en-y gastric bypass diet requires each day:

• 80 gm protein per day (preferably low fat sources).
• 1200 mg calcium per day (with 500 mg magnesium and 400 mg vitamin D – both help calcium absorption)
• 2 multivitamins with iron per day
• 500 mcg B12 sublingual
• 6-8 glasses of fluids per day (non-caloric beverages)

Note: What protein a patient can handle varies from patient to patient. I have no problem handling all forms of protein, but beef and tough meats require more chewing.