The Roman remains/ruins are in and around the attractive little town of Caerleon. We parked in the car park of the Bull Inn (you have to pay) and looked at the roman baths exhibit which is in a purpose built building and very well presented. Then we walked up to look at the amphitheatre and the barracks. Both of these have some remaining brickwork but are largely grassed over so you have to use your imagination a bit, but they were still really interesting. Finally we walked back to the actual museum building, which is fairly small but fits a lot of very good exhibits in, including a reconstruction of a Roman soldier barrack room. There's also a beautiful herb garden in a Roman style with plants they grew, which was a pleasure on a sunny day.
Very well worth a visit if you're in the Cardiff/Newport area or passing by and it's completely free, although they happily accept donations. Come off at J26 of the M4, then follow signs to Caerleon (a little confusing as you basically double back on yourself).
If you own or manage National Roman Legion Museum, register now for free tools to enhance your listing, attract new reviews, and respond to reviewers.