Oryza coarctata is the only halophytic relative in the genus Oryza (Oryza sp.) that is tolerant to high salinity levels lethal to cultivated rice varieties. An excessive accumulation of reactive oxygen species (ROS) caused by salinity leads to oxidative stress, although certain ROS also play important signaling roles. This work investigated differences in root redox and ionic homeostasis between cultivated (O. sativa) and wild (O. coarctata) rice species. Root treatment with 10 mM H2O2 decreased cell viability in cultivated but not wild rice, and histochemical staining showed greater H2O2 accumulation in wild rice roots under non-saline conditions, suggesting a signaling role. Wild rice showed higher superoxide dismutase (SOD) activity that lowers superoxide (O2-) accumulation. Cultivated rice showed greater K+ loss from the root mature zone through ROS-activated cation channels accompanied by stronger Ca2+ uptake in response to H2O2 application, while wild rice possessed better Ca2+ homeostasis with less H2O2-induced K+ leakage. Cultivated rice also demonstrated much higher sensitivity to hydroxyl radicals (●OH). Wild rice effectively controlled cytosolic Ca2+ homeostasis by Ca2+ efflux systems such as Ca2+-ATPase and CAX, while cultivated rice downregulated RBOH expression that may affect operation of the “ROS-Ca2+ hub” and signaling cascades under salinity.