I just laned against a Ryze and as soon as he hit level 6 he 100'd me in 1.5 seconds and I absolutely did not see this coming. He just flashed, stunned me, and then all of a sudden I'm dead before I could get out of the stun, from full health. Pre 6 I had no issues at all and I was up by 30 cs. Came back to lane and tried to harass him thinking his ult was on cooldown and then he stunned me and 100'd me again before I could get out of the stun.
So.. what the hell?
Yeah, Ryze excels against anything that has to get within melee range. Since Yasuo is squishy, melee, and lacks the burst of a true assassin, there's not much to do other than keep your distance and harass from range.
Consider delaying your core items for a set of Merc Treads and/or a QSS.
That seems pretty brutal.
I'd recommend playing ~10 Ryze games to discover whatever weaknesses he has and try to turn those against him. As a 450 IP champion that shouldn't be to hard to deal with and you could just run Co Op until you feel you get a good understanding of how he works.
At least with that knowledge you should probably be able to loose lane gracefully or at least go even.
Best guess is probably controlling the wave as Ryze's wave clear is a little "meh" without his ult up, and forcing him to ult to deal with minions rather than ulting you is probably a good thing. With Yasou's AoE wave-clear fast-shove techniques could be implored to roam to other lanes to get a lead Katarina style.
You wait for Ryze to get nerfed or get ganks. Those are your options. Obviously you can windwall when his passive activates that might save your life, or it might not.
Ryze doesn't have a stun.
Wait for patch 6.3
Windwall should save you, no? Blocks his Qs and Es for the duration of his passive, meaning you'll only be damaged by his W.
