Crossing the bridge to the south - near the eventual site of Fort Beausjour - was irrelevant. "There was no there, there". And if transit was needed to the communities to the northwest (Pre de Bourque, etc.) then this could be done by boat.
However, there has been some argument that Roger's Bridge might be at the present site of the Mount Whatley / Eddy Road Bridge (map below right). The river did narrow here, there was an historic road and relics (pipe stems, buttons, musket balls, etc.) have been found there.
But in my research I came across something that might account for this confusion (I don't claim being the discoverer of this but have not seen this observation reported elsewhere).
The British built another bridge to facilitate their travel between Fort Lawrence and the newly renamed Fort Cumberland. This cut travel time in half compared to going all the way to Rogers Bridge.
This observation seems to confirm the belief held by Colpitts, Trueman and MacKinnon who have spent lifetimes on the marshes studying its ecosystem and history.