Did ancient Romans have crucible steel, or techniques to enhance carbon content of iron to the point of being near steel? (such as repeated case hardening and folding the high carbon exterior in to expose fresh iron to the reducing atmosphere of a bed of coals)
If they had steel, would a common soldier's blade be steel, or would it be something officers purchased for themselves? Of course the Republic and Empire were large and covered a long span of time, do we know if ironmaking changed over time, or was better in some areas? Finally, how good are our written or archaeological sources?
It may help to know what definitions of iron and steel you are using. Does any amount of carbon make it steel, or does it need to be above a certain threshold? I'm a bit rusty on this (sorry for the bad pun), but I know that different definitions are used and perhaps you would classify everything below as steel.
I think of crucible steel as a South Asian technique in the ancient world. The Romans would have had methods of enhancing the carbon content of iron and were capable of making steel. RF Tylecote's A History of Metallurgy has a chapter on the Roman Iron Age that might answer a lot of your questions.
If you can get your hands on it, JE Rehder has an article titled, "Iron versus Bronze for Edged Tools and Weapons: A Metallurgical View" (Journal of the Minerals, Metals and Materials Society August 1992 (44.8): 42-46). I'll quote one part that you might find interesting: "A review of 507 such analyses shows that carbon contents of iron artifacts over the period spanning the 2nd millennium BCE to Roman times were largely in the range of about 0.1-0.9%. A range of about 0.3-0.6% carbon would include a considerable majority of the iron made in antiquity." (page 45). The main point of the article is to help archaeologists get a sense of the different ways that metals could be worked to achieve different sets of properties. Everything has advantages and disadvantages. He argues that the reason why carbon contents were typically in that range wasn't necessarily because of expense or because people were unable to achieve higher carbon contents. It was that making full-on quench-hardened steel had some drawbacks. People were typically using iron with this amount of carbon (0.3-0.6%) because that was what fit their needs and that was what worked best in their social context. You also have to think about who the blacksmith was and how a person (or soldier in the case of your question) could sharpen and take care of their weapon or tool. Rehder claims that at these lower levels of carbon content it would have been relatively simple to sharpen or rework a sword edge, but that a quench-hardened steel sword would need a skilled smith with a forge to properly sharpen and harden it (page 46). I don't know much about Roman period Europe, but since Rehder includes it in his survey of published analyses it seems he thinks that those would have been genuine concerns and perhaps reasons why low-carbon iron was used.
Something to keep in mind is that of the iron artifacts that are found, only a small percentage are analyzed for carbon contents and things like that. So, even when we have a lot of iron artifacts from a given time and place, we may not know what their carbon contents are. As far as texts are concerned, just remember that the categories that we make in our language are often different from the categories other cultures make. I know that translating metallurgical terminology can be tricky since there often isn't a one-to-one correspondence between categories of metals and alloys in two different languages (at least with what I've worked with in the ancient Near East).