Determinant stays the same after matrix transposition (i.e. row vector matrix would produce the same determinant as column vector one).

Should probably make it clear that the matrix is being represented by row vectors (alternative would be column vector). One can assume that and infer that from the examples but it really is the kind of info that should be in the instructions.

Bit of an inconsistency: instructions state you it should return an array of arrays, but the test (and attempt) cases expect a list of lists.

You went beyond and implement a RotN. I liked it.