( DROLL      rotates the n-th number onto the top of the stack )

need roll
: droll                           ( n --- d )
  2 *                             ( leave index to hi 16 bits)
  dup 1+                          ( leave index to lo 16 bits)
  roll                            ( rotate lo 16 bits to top)
  swap roll                       ( rotate hi 16 bits to top)
;