I don’t know where you saw that Red Rock Flat has water. If you could please give the SGWA website link or document you saw that states that.
Red Rock Flat Camp has no water. I would get water at Dry Lake on the way up to Red Rock Flat. Otherwise from Red Rock Flat Camp the nearest water is at High Meadow Springs which is just south of High Meadow Spring Camp and about 1 mile from Red Rock Flat Camp which is fairly level except for the 150ft drop in elevation to spring from High Meadow Springs Camp camp. Or Dollar Lake is about 750ft drop in elevation from Dollar Lake Saddle and a 1.5 mile from Red Rock Camp.