The bishop is in danger and unsupported no matter where you move it.

What I meant with giving check with the rook was:

1… Bxf4 2. Kh1/Kg1 Ra1+

That puts white in check with the rook, forcing the king to move, followed by b1Q. If then white takes the new queen at b1, she is protected by the rook at a1. Again, not the most elegant solution but at least black is not giving his promoted pawn away for nothing