I believe these Romans are cavalrymen, as they are reputedly wearing Roman Cavalry helmets. This is around the second half of the 3rd Century AD.
These are infantrymen. They adopted these helmets around this time for the infantry as well.
Yeah I actually found that out. I was looking at some books about the Roman Army and some still said that they were only Cavalry helmets. However, other sources have said that it was discovered that the infantry used them as well. Specifically around the time of the 200s AD, or the "Century of Crisis," for the Roman Empire.