I agree that the roads were helpful in the gathering of the troops of both Armies to Gettysburg.

But again Meade had already dismissed Gettysburg as a place where he wanted to give battle when he issued The Pipe Creek orders for the Army to congregate at that location. The Gettysburg roads were not needed for any part of the Union army to obey this order. Meade wanted to give battle at a more favorable position and closer to Washington. So why advance his army to Gettysburg?

Also the High Ground on Culp's Hill, Cemetery Ridge and later the Round Tops, was not even the scene of the 1st days battle. It was Gen Howards foresight which kept one of his brigades on Cemetery Ridge as a reserve and a fallback position. It was Howard and Hancock who organized the Cemetery Ridge line.

Buford knew of this high ground because he had passed throght Gettysburg the day before. Yet he chose to establish his defensive line on ridges outside of town rather than Cemetery ridge. So he chose that ground outside of Gettysburg as a battlefield over the "High Ground" which would become so famous.

Also Meade upon his arrival on the night of the first had a big discussion on whether or not to withdraw. So the roads were evidently not that important if Meade was willing to abandon them after the first day.