Though not wanting to be a 'party-pooper', but I wonder if this is a good place to put this modern piece of folklore to bed?
Lets look at the facts about it being a portion of Roman Watling Street.
The portion of supposed road was uncovered by a builder lowering the floor of the cellar of 48 High Street to make the basement into a more useable room. At no point during this scheme was an archaeologist, or a heritage professional, engaged to monitor the works, and thus no formal report has been produced. Because of this, no formal proof of stratigraphic sequencing, or dating (coins, pottery etc.) been produced to verify its authenticity. Constructed of roughly ashlar limestone blocks, some of which still possess evidence of diagonal tooling on their exposed upper face (the walking surface?). However, the local and national press have reported it as being a portion of Roman Watling Street, all of which is being absorbed by the general populace as a fact.
Lets look at the facts against it being part of Roman Watling Street.
Either side of the basement at 48 High Street, two formal archaeological excavations did encounter what has been interpreted as parts of Roman Watling Street, where the upper surface of a typical Roman road was revealed, but at a greater depth than that exposed in the basement of 48 High Street. In these two separate excavations, located at 49 and 54 High Street, the road consisted of the uppermost surface to a sequence of highly compacted, mainly laminated flint gravel with thin spreads of crushed chalk and silt between, all of which possessed dateable material including it fitting in with a surrounding stratigraphic sequence of Roman archaeology sealed by later deposits. Having worked on many Roman roads across Kent, this method of road construction conforms with that repeatedly seen, especially when passing through towns (Canterbury, Dover, Rochester, even London). As far as I am aware, unlike places were good quality stone is available (Yorkshire, Cotswolds etc.) this is a typical method of road construction with successive stone gravel road surfaces laid over previous worn-out surfaces, each possessing layers of trampled mud and silt encased between the gravel surfaces.
Is it possible that the stone blocks are Roman? There is every possibility they are and have been salvaged at a later date from an adjacent structure.
Do they make a surface to Roman Watling Street? Unlikely, as they are above the level of the road surfaces encountered either side of 48 High Street and the surviving stone tooling, as well as the blocks themselves, would have been heavily worn due to the amount of cart, animal and foot traffic over a prolonged period of time.
So what is exposed in the basement of 48 High Street, Rochester and so poorly interpreted and reported? In my opinion, what is exposed in a very expensive display case is a portion of the period building's basement floor, itself formed from possibly reused/salvaged Roman (or later) stone blocks.