The objective of the present study is to investigate the buoyancy effects induced by various body forces in non-isothermal rotating fluids. The buoyancy effects stemmed from the gravity, the centrifugal and Coriolis forces generated by system rotation, and the curvilinear motion of the fluids are all taken into account. Mixed convection between two disks rotating at different rates is employed as the physical model. The present work is the first study for detailed investigation of the various buoyancy forces in the class of non-isothermal flows. Complete system of axially-symmetric thermal flow model with assumption of Boussinesq fluids is formulated. By a scaling analysis and the solutions of a novel similarity model developed in this work, the relative importance of the buoyancy effects induced by various body forces is explored. The present work discloses the significance of the rotation-induced buoyancy effects under various conditions and is useful in understanding the mechanisms as well as modeling the mixed convection heat transfer in the class of rotating thermal flows.