Low-frequency turbulence and the resultant cross-field plasma transport in mirror-based systems are studied by means of direct computer simulations of nonlinear plasma dynamics. Under the low-beta assumption the nonlinear dynamics are simulated in a frame of adiabatically reduced one-fluid MHD model. Simulations of self-consistent plasma evolutions have shown formation of large-scale flute-like stochastic vortex structures, which have broad-band frequency and wave-number spectra and are similar to the intermittent vortex-like structures observed in GAMMA 10 experiments. Simulations were performed both for the conventional tandem mirror configuration and for axisymmetric non-paraxial configuration with divertor-like separatrix. Various regimes of plasma confinement with sheared plasma rotation have been modeled and analyzed.