On arriving in Philadelphia Rosbrugh's company joined the rest of the Northampton county militia in camp. John Rosbrugh was able to dine with his brother-in-law, John Ralston, a member of the Second Continental Congress. The 3rd Battalion was under the command of General Israel Putnam who had orders to cross the Delaware on the 25th of December in support of Washington's surprise attack on Trenton; but Putnam decided not to cross due to weather conditions so Rosbrugh's battalion remained in Philadelphia. After General Washington crossed back to Pennsylvania, with his Hessian prisoners and captured goods, he decided to take Trenton a second time. This time the 3rd Northampton militia was included and arrived in time for the second battle of Trenton, also known as the battle of Assinpink creek.