In the PA Archives link I gave you, a Cornelius Best and a Thomas Best were each issued certificates for depreciation pay (IOUs for money owed for active duty service).They were listed in Westmoreland County.It is possible they went on the May-June 1782 expedition into Ohio known as "Crawford's Defeat," but the depreciation pay certificates do not spell out what the service was.
Try the published PA Archives, vol. 5 and vol. 6 which have rosters for this expedition in very disorganized and not well-identified form.
I did not see a listing for a Robert, but that does not mean he had no service.