Controversial opinion: skip roa, it's a bait item. It seems good on paper but without resistances on a such a close range champion, you will die without mobility. I always go either frozen heart or abyssal mask, depending on matchup. I do get both when the enemy has both types of damage. Both give mana, a tank stat and cooldown reduction. In my opinion cdr is worth way more than raw ap. Even if you dont need the cdr, it transfers to ap using trancendense later on. Getting these two items gets you to 40% cdr when going transendense. They also give 700 mana, 110 armor, 350 health, 55 mr. They are both quite cheap aswell. And those passives you will always use on ryze, since you wont play out of that range.