Due to her reptilian nature, Mamba lived a solitary existence for most of her life. She's tried to make friends, but the people of Arcadia have a deep seeded fear of snakes. That is until they started being attacked. Now even snake-like beings are welcome in battle, even if she does still make some people nervous.
Rosh was once a brilliant alchemist, but after losing his arm, he combined his blood with a lizard. The experiment was a success. . . to a degree. His arm was regrown, but it turned Rosh into a reptile. His regenerating powers make him a useful ally to the Heroes.