Does this theory make sense? No. Not at all. Am I still going to share this theory? Yes. Yes I am.

Roman used to be a 'Dark Side' (I won't be using a list format for this)

Roman's always been quite protective over Thomas. This behaviour has also been seen with other 'Dark Sides' such as Virgil and Janus. He's also seeking some kind of reassurance from Thomas or the other Sides. Some sort of reassurance that he's not who he used to be. That he's been accepted as a 'Light Side'. Also, the only people who have called the 'Dark Sides' 'the others' is Virgil (a cannon 'Dark Side') and Roman. Roman was also the person to introduce the 'Light Side' and 'Dark Side' names, therefore making the difference between the 'Lights' and 'Darks' even more pronounced. In Selflessness vs Selfishness, Roman seemed very won-over by Janus' argument. What if this was because he trusted Janus in the past? And then in the Redux episode, he acted how someone might expect Virgil to act around Janus. He hated him and made fun of his name. I think that him making fun of Janus' name could've been a reflex like giving Virgil a 'cruel' nickname. It's just something he does to further himself from the other 'Dark Sides', showing that he's not like them anymore. Roman is also the only Side to wear white. White is, as we all know, the opposite of black. All 'Dark Sides' wear black. This could be another way Roman's distanced himself from 'the others'. Roman was also the first 'Light Side' to mention the 'Dark Sides' in passing. In Accepting Anxiety Part 2, he says "You're better than the others." or something along those lines, it not a direct quote. He's the first Side, 'Light' or 'Dark', to acknowledge the 'Dark Sides'. Roman's also shown some quite 'Dark Side' like tendencies. He's quite prideful and confident in what he does, like Janus. He's very stubborn and doesn't back down, even if it ends up hurting Thomas, like Virgil. And he doesn't think things through very well, like Remus. He assumes that everything will go the way he plans it, just because he plans it.

Tell me what you think of my theory in the comments.
Bye,
Queenie