Yes, it's a draw. Either side can force a draw in case the opponent doesn't agree.
To checkmate with a rook and king, you need your king to be on the c or f file if your opponent's king is on the a or h file, or on the 3rd or 6th rank if the opponent's king is on the 1st or 8th rank. So to prevent being checkmated, it's enough to separate the opponent's king from yours with your rook so that your king has 2 ranks or files to the end of the board to maneuver and to make sure your opponent's king doesn't attack your rook. Your opponent will be unable to make progress. This way you can force the 50 move draw rule, the threefold repetition rule or the insuffficient mating material rule after a rook exchange.
Here's a way how White could force a draw (Black can do it in a similar way):
We agreed on a draw on this game. We each had one rook and nothing else. Is that a good idea to agree on a draw. It seemed like that was really the only option.