I’ve sorted the characters according to their introductory affiliation.
Anteiku/Re Affiliates
Kaneki Ken – bisexual
Nagachika Hideyoshi – bisexual
Yoshimura Kuzen – straight
Kamishiro Rize – pansexual
Kirishima Touka – straight
Koma Enji – bisexual
Irimi Kaya – bisexual
Yomo Renji – gay
Kosaka Yoriko – straight
Hinami Feuguchi – straight
Nishiki Nishio – straight but curious
Nishino Kimi – straight but curious
Tsukiyama Family
Tsukiyama Shuu – pansexual
Karren von Rosewald – Tsukiyama-sexual
Matsumae – lesbian
Mirumo – pansexual
Chie Hori – asexual
Clowns
Uta – bisexual
Itori – straight
Hoito Roma – straight
Nimura Furuta – he says he is straight, but insists a bit too much.
Rio/Shikorae – bisexual
Nico – bisexual, leans towards men
Donato Porpora – straight
Aogiri Tree
Kirishima Ayato – straight
Yamori – gay
Tatara – gay
Yoshimura Eto – bisexual
Noro – straight
Miza Kusakari – straight
Naki – straight
Hakatori – straight
Banjou Kazuichi – straight
CCG
Amon Koutarou – straight
Takizawa Seidou – straight
Mado Akira – straight
Houji Kousuke – gay
Mado Kureo – straight
Marude Itsuki – gay
Washuu Yoshitoki – bisexual
Washuu Matsuri – gay
Washuu Tsuneyoshi – straight and extremely insistent upon that.
Kuriowa Takeomi – straight
Kuriowa Iwao – straight
Aura Kiyoko – lesbian
Tanakamaru Mougan – gay
Shinohara Yukinori – straight
Itou Kuramoto – bisexual
Kurona Yasuhisa – demisexual
Arima Squad
Ihei Hairu – straight
Arima Kishou – bisexual
Ui Koori – straight
Take Hirako – bisexual
Suzuya Squad
Suzuya Juuzou – pansexual
Keijin Nakarai – straight
Hanbee Abara – gay
Miyuki Mikage – straight but curious
Mizurou Tamaki – straight
Quinx Squad
Yonebayashi Saiko – bisexual
Shirazu Ginshi – straight
Urie Kuki – gay
Mutsuki Tooru – gay
Hsaio Ching-Li – lesbian
Aura Shinsanpei – straight
Higemaru Touma – straight
Mercy and Magic 