All movement Speed bonuses are 8% more effective on you.
+5 AD or 9 AP
+6 Armor or 8 MR (match-up)
Unsealed Spellbook on Ryze allows you to run a various number of Summoners in the mid lane (Cleanse, Ghost, etc.) depending on your matchup while still being able to swap to Teleport later in the game for more map pressure.
Magical Footwear's raw gold value is incredibly useful in the mid-game, account for nearly a kills worth of gold for that crucial 2 item power-spike.
Minion Dematerializer allows you to effectively wave-clear to match roam timing and get efficient recall timings off.
On Ryze you are able to Dematerialize->[E] and if the minion dies while your [E] is mid-air your [E] will spread as if you had killed it.
Cosmic Insight is an all-around fantastic rune choice for Ryze. The extra bit of CDR let's you pump out more DPS and the extra Summoner CDR helps keep you safe in the laning phase.
Manaflow Band synergizes well with Ryze's natural tendency to build up a massive mana pool. The missing mana refund will allow you to continue spamming in teamfights to pump out massive DPS.
Celerity's extra Movement Speed synergizes well with Ryze's [P] movement speed burst to help you position and kite in fights.