I can't see any tricks, so the obvious try is for White to get his rook to the b-file, preventing Black from getting his king out of the way of his pawn.
1. Rc5 a4
Then, with the king safely cut-off and no-way for the a-pawn to queen, White can wander his king over to h4 to support g4-g5. Once these pawns are on the move it's game over. If Black ever threatens to exchange rooks then White should instead swap his rook for Black's a-pawn. Once both of White's pawns are on the 6th rank they are worth more than a rook and one of them will queen without any problem.
One more thing - if Black gets his king on a1 and the pawn on a2, then White has to watch for stalemate tricks, so White will need to take the a-pawn before that happens.