Yes, let's mention Roman Law in relation to British Common Law. The latter derived from the former, but there's a fair distance of about 1,000 years between our three points in time.

For all intents and purposes, every precedent and matter of jurisprudence can be resolved by referring only to Common Law. It would be rather exhausting and absurd to try and reach back past 1066 AD because things have changed, a lot.

Now in terms of forking Roman Law, there are other legal systems which are not directly related or derived from British Common Law. Especially the Napoleonic Code, which influenced Italy, which in turn influenced Catholic Canon Law. So here we have another lineage and a deeper "fork" from Roman Law where British Common Law doesn't really figure.

Also someone commented with a non sequitir about "antidisestablishmentarianism". I'd just like to point out that that word refers to revocation of things like the 1st Amendment and support for the Established Church laws, because it's "anti-dis" double negative.

If you want to talk about the United States' 1st Amendment, "disestablishmentarianism" is the term used to describe how the Founding Fathers set up the States without those meddling bishops.