Good luck on sacrificing a non-existent rook ! 
Why Sacrifice the Rook?
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Lol. For some reason, the board cleared when I set it to "Black to play".
also questing that the knight is trapped
The position is lost for black: a piece down.
So it does not really matter.
AstroBullivant wrote:
In this pair of moves, Black effectively trades a rook for a bishop, which is usually an unfavorable trade. Why is it the right move here?
You are wrong. Blacks trades a rook for 2 minor pieces, not one. The white knight can't escape from a8 and will be lost.
You can click on the "magnifying glass" icon in the bottom left corner to open engine analysis, and you can try every move in there.
@tygxc,
I believe I forgot to put the bishop on e7 in the original position. I have edited it. Sometimes, posting positions on here is frustrating because it keeps clearing the board.
AstroBullivant wrote:
Lol. For some reason, the board cleared when I set it to "Black to play".
I know, it's really annoying when it does that.
Black to play:
11. ... Black: Nf6-d7