Forced Mate or Draw? Rook v. Knight Endgame

My friend Shannon Huffman and I have just finished a refreshing game of chess.  In the endgame we got to this position:

Do we have here a forced mate for black, or a draw?  Furthermore, is it forced mate or draw because of this particular position, or because of the nature of rook v. knight endgames.  I know that in some positions, the owner of the rook can force a mate, but is this theoretically true in all rook v. knight circumstances?

-BRO