Chromedome (gay): Is married to Rewind. Had other husdbands before him and used to date Prowl too.
Rewind (gay): Is married to Chromedome. Before him, he was married to Dominus Ambus.
Cyclonus (gay): Falls in love with Tailgate.
Tailgate (gay): Falls in love with Cyclonus.
Brainstorm (gay): Fell in love with Quark but it was unrerquited. Heavily implied he has feelings towards Perceptor. Then confirmed by JRo at the end of LL.
Perceptor: Any interaction with Brainstorm during and after the Time Travel arc heavily implies he has feelings for him. Hints go until being confirmed in the ending of LL.
Drift: Have ship tease with both Rodimus and Ratchet, Lug and Anode mistake Rodimus for his boyfriend,and had bigger hints with Ratchet. Gets with Ratchet at the end.
Ratchet: Cares a lot for Drift and is implied to be attracted to him. Canonized as the ending of LL.
Skids (bi): Flirts with Firestar not realizing she is a "she" and not a "he" but doesn't change his opinion on her. Had romantic feelings for Nautica but that arc was dropped for a platonic one.
Pipes (gay): Flirted with Drift as he explained him his very specific type and his interest in getting in a relationship (during a time there were only men in the ship), shown interest on Tailgate, had a crush on Riptide.
Prowl (gay): Chromedome's ex.
Getaway (bi): Like Skids, he also Flirted with Firestar and seems to don't have problem flirting based on gender.
Anode (trans lesbian): Changed her body after leaving her planet and realizising she is a girl. Married to Lug.
Lug (trans lesbian): Trasn girl, didn't changed her body. Married to Anode.
Crankcase (gay): Has an internet alien boyfriend (cons4eva - right).
Cons4eva (gay): The internet boyfriend.
minor characters: Dominus Ambus (Rewind's first Conjunx), Proxima (Married to a lady),
____Hinted in canon / but only confirmed by word of god____
Rodimus: It's implied he is attracted to Drift, Anode mistook them for a couple, so apparently implied Magnus, when asked if Rodimus would officiate the Drift/Ratchet wedding JRo answerd "There was a conflict of interest". The LL ending shows him supportive of Drift relationship with Ratchet. JRo confirmed him and Drift were more "friends with benefits".
Ultra Magnus (Minimus Ambus): It's implied he is attracted to Megatron, Rodimus thinks they're a couple, when asked if Minimus had a crush on Megatron, JRo answerd "only if life were this simple", script comments mentions he wanted to be held by Megatron in the christmas comic.
Megatron: Had ship tease with Ultra Magnus (read above), some of his interaction with Optimus can be read as romantic.
____not mentioned in canon, but confirmed by JRo____
Cerebros, Fortress Maximus and Red Alert (gay): Confirmed to be a poly relationship.
Nickel (bi): Confirmed she had a girlfriend back then in her planet. She is shown flirting with Roller too..
____IMPLIED____
Roller (bi): Shown rather touchy feeling with Springarm during the little pages they're together. But he also flirted with Nickel.
Springarm: ^
Optimus Prime / Orion Pax: It's implied was in a Relationship with the Senator Shockwave
Ten (gay): Implied to have a crush on Ultra Magnus.
Whirl: Consideres Chromedome, Rewind, Rodimus, Cyclonus, Tailgate and Rung attractive, but haven't shown romantic interest in any of them.
Swerve: Has a crush on Blurr, but Skids calls it a "celebrity crush".
First Aid: The way he describes Sringer heavily implies he has a crush on him.