Freshwater scarcity is a growing concern worldwide, particularly in arid and semi-arid regions, creating an urgent need for alternative irrigation resources. This study aimed to evaluate the potential of treated wastewater (TWW) and untreated wastewater (UWW) for sustainable ornamental horticulture using Rosa centifolia and R. Gruss-an-Teplitz as a test species. A two-year field experiment was conducted in which plants were irrigated with canal water (CW), TWW, or UWW. Water quality analysis showed that CW and TWW were within the permissible irrigation limits, whereas UWW exceeded the thresholds for Cd, Pb, Na, nitrogen, biological and chemical oxygen demand. UWW application significantly reduced root length, biomass, photosynthetic pigments, gas exchange attributes, and antioxidant enzyme activities, while increasing malondialdehyde, H2O2, and electrolyte leakage. In contrast, TWW improved root length (34-50%), photosynthetic pigments (8-44%), gas exchange (6-55%), antioxidant enzymes (20-143%), sugars (12-140%), and phenolics (40-93%) in both species compared to the control group. These results highlight the suitability of TWW as a nutrient-rich, environmentally safe irrigation alternative that supports ornamental plant production and offers commercial and ecological benefits in water-stressed regions.