Hi Ghost of Clayton,
I've looked at your list and can add some more to it. I'm curious as to why you are excluding Roman sites that are free to visit. There are some incredible sites that I would recommend visiting that are free - Hardknott Fort on top of Hardknott Pass and Caerwent(Venta Silurum) town in Wales for instance.
Anyway here are my contributions:
Forts - Binchester, Chesters, Ribchester
Museums - certainly Corinium in Cirencester, also Roman Museum in Canterbury, Senhouse Roman Museum in Maryport, St. Alban's Verulamium museum (has some great mosaics), Roman Legionary Museum in Caerleon, Camulodunum/Colchester Castle - has a lot of Roman exhibits but not exclusively Roman
The Roman theatre of Verulamium in St. Albans also charges an admission.
The Jewry Wall in Leicester is free to visit but the attached museum charges an entrance fee (it is exclusively Roman but fairly small).
About Caerleon and Caerwent in Wales: the sites of the barracks and the amphitheatre are free to visit, as is the museum but the Fort Baths has an admission charge. Caerwent is a town site that is free to visit (the town's walls go almost completely around and are very high) but there are no Bath ruins there (which you have on your list).
Silchester (on your list) is free to visit and there are no facilities there for visitors (at least there wasn't when I visited 4 years ago).