8... Rf1 is poor. Black can last longer with Rg4 or Re4.
I don't have time for a full analysis, but black would be in a kind of zugzwang after 1.d4 here- the black rook can't leave the f-file or the 4th rank, black can't move the h-pawn. If black plays 1...a5, white just plays 2.Rg1 and the black king will have to retreat to the 8th rank and get trapped there after 3.Rg7- then white puts the rook behind the h-pawn to keep an eye on it. After that point, white brings the king over to e3 and drives the black rook away from the 4th rank or the f-file, either of which loses. This is the line I have in mind:
9.Rxh4 the rest is pretty easy.