A moderate amount of food in your stomach shouldn't ruin the roll.
In the future, avoid carbs...stick to protein.
I recommend eating several hours prior to rolling. It is important to have something in your GI to slow down the rapid absorption of the drug from the intestinal wall.
Having an empty stomach and intestines can lead to a VERY fast and unpleasant come up.
Remember, MDMA and all serotonin agents are targeting the nerves that connect the intestines to the brain. That's what the serotonin system IS - the 'brain-gut' connection.
Treat your intestines kindly when taking MDMA.
Also, understand that MDMA has been proven to cause long-term/permanent alterations in this 'brain-gut' circuitry. It has also been proven that this change is dose-dependent. The more you take, the more damage is done.
The best thing you can do for your intestines and your brain is to space your rolls and avoid re-dosing.
Good luck.