I started out alright but he kept snaring me and htting me with skills, getting me below half hp with one combo. It got really bad and he was doubling my CS. Any advice?
Ryze's snare > Your silence. As long as he estimates the cooldown on your combo (incl. silence), a good Ryze will shut Kassadin down any time. Ryze can't 1 vs 2, so next time call for ganks often and he will snare one of you, and be vulnerable to the other. I main Ryze and believe that I win mid lane 90% of the time and top 80%.