With the defending king in front of the pawn, put the rook on the third rank (from the attacker's point of view, the sixth) to keep the enemy king out; when the pawn advances to that rank, drop the rook to the back rank and check from behind.
The basic drawing method against a pawn on the fourth or fifth rank when your king is in front of it. White's king on d5 wants to reach d6 or e6; if it gets there with the pawn still behind it, Black is in serious trouble.