  We study the Roberge-Weiss phase transition numerically. The phase transition
is associated with the discontinuities in the quark-number density at specific
values of imaginary quark chemical potential. We parameterize the quark number
density $\rho_q$ by the polynomial fit function to compute the canonical
partition functions. We demonstrate that this approach provides a good
framework for analyzing lattice QCD data at finite density and a high
temperature. We show numerically that at high temperature, the Lee-Yang zeros
lie on the negative real semi-axis provided that the high-quark-number
contributions to the grand canonical partition function are taken into account.
These Lee-Yang zeros have nonzero linear density, which signals the
Roberge-Weiss phase transition. We demonstrate that this density agrees with
the quark density discontinuity at the transition line.
