Is it possible to checkmate if all you have is a rook and your opponent only has a knight? If both of you play without mistakes or blunders?
When you have a Rook & King vs Knight & King then in most cases the Game would be a draw if played with Best play . Now the Person who has got the Knight he is to make sure that the Knight does not get separated from its King . The Rook should try pushing the King either on the 1st or 8th Rank or a-file or h-file. The Opponent King should try centralize himself . If also the King reaches any of the four Corner ranks or files then the Knight should stay close with the King . The Knight always hinders the Checkmate pattern and comes between the Rook & King .
In this kind of play it is the focus & attention of the Knight Player that plays the role because he is to make sure that Knight does not go far from the King where sometimes it gets trapped and the Game gets Lost.