Players should be able to communicate that they no longer believe further moves can be made at the end of a round, and when both agree the round should be ended. When there is disagreement, that should be transmitted to both players to allow them to continue making moves.
When the first round is ended, a second round should be started with players races reversed. At the end of the second round, the game should be scored and that score returned to both players.
There is no way to end a game, or a round.
Players should be able to communicate that they no longer believe further moves can be made at the end of a round, and when both agree the round should be ended. When there is disagreement, that should be transmitted to both players to allow them to continue making moves.
When the first round is ended, a second round should be started with players races reversed. At the end of the second round, the game should be scored and that score returned to both players.