Need help going against melee mid as Ryze

I am totally fine going against your typical ranged ap or random ad people, but I literally ALWAYS lose mid when I'm against melee champions both ap like Katarina and ad like Zed. Any tips? My usual only saving grace is that my ganks and roams are still effective but mid always gets pushed in and in that case I end up relying on a fed top or bot carrying the game.