Hi,
I don't believe that portrait was done first hand. Major Rogers was feted in written accounts and broad sheets at the time, particularly after the St Francis raid. Ironically, he thought the raid a failure because he lost so many men but the English public treated him as a hero. The documentation is confusing and I think we have to recognize that ranger units were not armed uniformly. Moreover, they were not universally supported by the British Army. Some commanders thought them undisciplined, expensive, and not worth the effort or expense. Others valued them highly. What records exist suggest they may have carried pattern 1730/40 and pattern 1742 long land muskets, full length or with older ones shortened. Some records suggest units might be issued the mysterious "carbine" often linked to Highland units. There are references to some rangers having rifles and others using captured French muskets that were prized as light and handy. I think a reenactor can take quite a few liberties and disregard anyone saying it was "just so".
dave