Drought (water shortage) can substantially limit the yield and economic value of rose plants (Rosa spp.). Here, we characterized the effect of exogenous calcium (Ca²⁺) on the antioxidant system and photosynthesis-related properties of rose under polyethylene glycol 6000 (PEG6000)-induced drought stress. Chlorophyll levels, as well as leaf and root biomass, were significantly reduced by drought; drought also had a major effect on the enzymatic antioxidant system and increased concentrations of reactive oxygen species. Application of exogenous Ca²⁺ increased the net photosynthetic rate and stomatal conductance of leaves, enhanced water-use efficiency, and increased the length and width of stomata following exposure to drought. Organ-specific physiological responses were observed under different concentrations of Ca²⁺. Application of 5 mmol · L⁻¹ Ca²⁺ promoted photosynthesis and antioxidant activity in the leaves, and application of 10 mmol · L⁻¹ Ca²⁺ promoted antioxidant activity in the roots. Application of exogenous Ca²⁺ greatly enhanced the phenotype and photosynthetic capacity of potted rose plants following exposure to drought stress. Overall, our findings indicate that the application of exogenous Ca²⁺ enhances the drought resistance of roses by promoting physiological adaptation and that it could be used to aid the cultivation of rose plants.