How many calories did Roman Legionaries eat?!

Roman soldiers ate about 800-1000 grams of grains daily, thus it appears that an average Roman soldier consume 3000 calories of grains alone per day, as that specific form of food covered at least 80% of a soldier's daily diet especially during campaigns; wheat, barley, and oats, mainly, and also spelt and rye, which they made into loaves of bread and baked them on their own with the help of iron skillets which had always been an important part of their inventory. But these number might be misleading as many historian has questioned the claim that Roman soldier didn't ate any meat, they believe it was not because they specifically refused to eat meat dishes, but caused by their need for high quality protein and to limit the amount of food they had to carry, so grains were preferred than meat. Recent history, epigraphy, and archaeological findings strengthened the hypothesis that Roman soldiers throughout the Republic and Empire ate meat regularly.

"The Roman Military Diet" by R.V. Davies

"The Warrior Diet: Switch on Your Biological Powerhouse For High Energy, Explosive Strength, and a Leaner, Harder Body" by Ori Hofmekler

I don't think that's known and I doubt that will be known from archeological evidence. Perhaps your question would be better in anohter categori.