The historical Roach Belly knife was a short blade with a pronounced upswept curve and a sharp point.
It was most likely named after the common Roach Fish, which had a similarly round curving belly.
The
English Trade Knives were modeled after the other straight-forward English trade goods of the period.
Although the trade knife handles are usually of hexagon form, rather than the rounded form of the French drop points, the Roach Belly knives had a rounded handle..
The Roach Belly pattern was known in 17th century Britain, and also quite common in the American Colonies because it was inexpensive and versatile.
Most have a rather short (IMO) blade, around 4-1/2"-5", but I prefer the earlier versions, which had a larger (6"-7") blade.
I re-handled one of the shorter versions in Stag/Ebony, and it's just right for skinning.
T.O.T.W. carries a repop English Roach Belly Trade knife:
https://www.trackofthewolf.com/Categories/PartDetail.aspx/464/2/KNIFE-ROACH-4
There are also many other makers/vendors.
This one is from Townsends:
https://www.townsends.us/collections/axes-knives-tomahawks/products/roach-knife-kn