A few points on roll casting. First many weight forward lines are not designed for roll casting. Also a short leader will turn over easier.A stiff but leader is better then a soft but section. Look for a .22 then a .20 but and so on. Also any weight added will deter from good casting. Fly rods are designed to cast a line and the fly goes along for the ride. Even small split shots and floats make it harder to cast. Perhaps try medium nymphs and wet flys. Bead head nymphs sound like a good starting point.