So, I'm reading the eagle series by Simon Scarrow, and the main character describes rat droppings as "rice-sized turds". The character is of equestrian class and a prefect in the roman military, and has been to some fancy dinners, but as i recall rice was never described in the books, exept from this one reference. Would it be plausible for him to know what rice is? Did rice play any role in roman quisine in 50 ad? I'm really curious about this for some reason..
Not in Roman food, but types of rice were grown in Mesapotania and Judea around that time (a little niche, its arguably mentioned in the bible, it is mentioned in Roman recordings), so its not implausable he may have known of rice. It's much more likely he would have reached for a different kind of grain as a descriptor.