  We derive general rogue wave solutions of arbitrary orders in the Boussinesq
equation by the bilinear Kadomtsev-Petviashvili (KP) reduction method. These
rogue solutions are given as Gram determinants with $2N-2$ free irreducible
real parameters, where $N$ is the order of the rogue wave. Tuning these free
parameters, rogue waves of various patterns are obtained, many of which have
not been seen before. Compared to rogue waves in other integrable equations, a
new feature of rogue waves in the Boussinesq equation is that the rogue wave of
maximum amplitude at each order is generally asymmetric in space. On the
technical aspect, our contribution to the bilinear KP-reduction method for
rogue waves is a new judicious choice of differential operators in the
procedure, which drastically simplifies the dimension reduction calculation as
well as the analytical expressions of rogue wave solutions.
