Unless one of the players makes a blunder it will be a draw
Rook and King

It will be a draw unless and until one blunders his rook or trapped due to not playing positionally.

The same is true of each player having a king and a bishop, or each player having a king and a queen. Assuming the start position is balanced (that is, not leading to an iimediate mate) then it should be a draw.

Thank you, guys. I especially found oinquarki's illustrations to be helpful.
Hello:
If each player has one rook and his king at the end, is it possible to mate or is that going to be a draw?