The statement "I will have to roll you in flour if you keep eating so much" is an idiomatic expression typically used in a playful or teasing manner. It is not meant to be taken literally.
In this context, it seems like your boyfriend is using the phrase to jokingly imply that you have been eating a lot or indulging in food. The phrase is often used as a humorous way to suggest that someone might be gaining weight or becoming rounder due to their eating habits. It's important to note that such comments should always be made in a lighthearted and consensual manner and should not be intended to hurt or demean anyone.
If you're comfortable with this type of banter and understand it as a playful remark, you can respond accordingly. However, if it makes you feel uncomfortable or if you believe it crosses a boundary, it's important to communicate your feelings to your boyfriend and express your preferences regarding the types of comments that are acceptable to you in your relationship. Open and honest communication is key to maintaining a healthy and respectful relationship.