This position comes from Fressinet-So, Round 6 of the TATA Steel Tournament 2011. So won a pawn early in the game, but it has not been easy for him since then. Here, we have a very instructive rook and multiple pawn ending.
If you follow the game from the beginning, as I did, it will be harder to realize that white is already lost at this point. That's why it has been suggested that we stop at the transition point from the middlegame to the ending and assess the position de novo. I know, we continually asses the position as the game goes on, but I am talking about wiping the slate clean and putting on a fresh new outlook. If you come into this game at this point, without knowing its prehistory, or being under its influence, then you will realize sooner that white is lost, barring a tremendous blunder by black.
First, black is a pawn up. Second, black has two pawn islands and white has three. White has three isolated pawns while black has three connected passed pawns. Black's G pawn is two squares from the queening square while white's c pawn is three squares away. The rook on c7 is in the way, and white has to spend a tempo just to get that rook out of there. Black does not have such a problem. Black's rook is behind his passed pawn and his H pawn is threatening to kick the white rook on g2 out of the way.
Play went 39. Ra7 h4 and the C pawn still cannot advance because of the rook on f6. Fressinet went 40. Ra3 but So's 40...h3 forces the win. The H pawn will be able to go past white's rook and promote, all this without the help of the black king, largely because the black rook is placed behind his pawn. Play continued 41. Rag3 Rg3 42. Rg3 h2 and white's rook check on h3 will not work because of rook to h6.