Foraging for soldiers included plundering and pillaging the local population. They could also just have easily hunted the local villagers' livestock as a source of meat which they could then salt and preserve for food on the march.
The article I listed explained in detail how Roman soldiers carried out the full process of turning grain into flour and then baking bread in their encampments. You don't think they could have managed the slaughtering of livestock?
But besides that, there were plenty of forests around (which they used to gather firewood, as mentioned in the article). Those forests absolutely would have contained deer and other game they could hunt and preserve.
In a previous comment, you wrote about Roman soldiers "hunting any game they came across". "Game" means wild animals.
Of course they stole and ate any livestock they could get unless they were passing through the territory of an ally, in which case the commander probably has warned the men that any man caught pillaging would be executed, but in compensation, the commander had probably purchased livestock and other food from the ally to be distributed to the men.
I did some more research. The Romans actually had dedicated hunting units attached to their armies, called venatores. They hunted wild game for food and also captured animals to return to the city for entertainment (venationes) and public executions (damnatio ad bestias).
So not only did they hunt, they made it a formal part of their military, not merely an opportunistic food source.
I have to say, I don't appreciate that you would take such an obstinate stance without doing any research of your own. It's intellectually lazy.
The article I listed explained in detail how Roman soldiers carried out the full process of turning grain into flour and then baking bread in their encampments. You don't think they could have managed the slaughtering of livestock?
But besides that, there were plenty of forests around (which they used to gather firewood, as mentioned in the article). Those forests absolutely would have contained deer and other game they could hunt and preserve.