A "mysterious" rook move, realizing that Black's only viable plan is ...b6-b5.
Some more prophylaxis in order to cover the sensitive second rank. Meanwhile, Black is just playing with one rook, since the one on f8 is tied to the defence of f5.
It doesn't seem right to abandon the seventh, but there weren't many moves to choose from.
In view of the coming Rc2-g2, Black protects the g7-pawn in advance and prepares a further reinforcement of the kingside by ...Bf8 and ...Ne7-f5.