I've been told its best to not eat DIRECTLY before rolling. A lot of people say this really decreases the effect, and I can attest to that as well. But you definitely don't want your stomach to be completely empty, this can cause nausea to some, increase neurotoxicity and probably have some other contraindications as well. I've also heard from some that not eating at all can make the comedown much worse. Which makes a lot of sense to me because your depriving your body of essential nutrients needed to make yourself feel well again afterwards, but i guess that could also by avoided by eating a lot directly after rolling. However, your body needs nutrition, especially before doing drugs, so just don't starve yourself. Eat a meal a couple hours beforehand.