Well, I see pretty solid rock evidence there with the combination of bricks similar to the flat square shaped ones of Romans and the fact that the bricks were burned which is even more unusual for America of that time.

Small correction: They are not really square shaped I see now when looking close at some photos, for example the one showing with brickwork in the image title in the middle of the Wikipedia article. But many Roman bricks are neither square shaped and some look exactly the same also with the thick mortar layer in between. For example on the photo from Leicester: [en.wikipedia.org]

Roman bricks in general are much flatter than the standard red bricks used in Europe and the US later.