A quasi-linear numerical model for RF heating is developed in a form so as to be applicable both to tokamak and to magnetic mirror plasma confinement devices. It is then combined with a two-dimensional multi-species Fokker-Planck code to yield detailed information on the distortion of the ion distribution function due to an imposed level of RF. For a two-component tokamak, it is found that while "fast-wave" ion heating will not increase the fusion output, as much as 40% of the beam power may be replaced by RF in a strongly driven two-component tokamak without significantly degrading the fusion output. For magnetic mirror devices, results indicate that RF in combination with relatively low-energy beams may be expected to heat the ions to well above the beam injection energy as well as to increase confinement.