Most (if not all) were bisexual or pansexual.
Sexual orientation of Greek gods was a different concept in ancient times. It can best be described as bisexual.
Not all roman people are/were gay. If you are asking how they became gay, it's because they were born with that particular sexual orientation.
The character of Flapjack is not written with sexual orientation
Nothing is known of her sexual orientation.
The Joker's sexual orientation is not written into his character.
Soko's sexual orientation is heterosexual/straight.
The sexual orientation of David Rodriguez is unknown.
Matt Evers' sexual orientation is not known.
The fictional character of Yoshi is not depicted with sexual orientation.
Frankie Muniz has not stated his sexual orientation.
The SNL character "Gilly" was not written with sexual orientation.
Reginald VelJohnson has not publicly spoken about his sexual orientation.