I would've written Roper off as a classic example of Dunning-Kruger effect, if it wasn't for the fact that he appears to be very much aware that he is entirely devoid of any magic skill. He is entirely useless, even as a Vanguard-pawn. Consider the way he behaves and interact with others, for example; childish, impatient, spiteful and entirely unable to control his temper.
Consider his response to April telling him she is not a wizard: 'Wizards. Frauds, the lot of them. The only real magic is the magic of alchemy.'
Oh yeah? Not according to Benrime Salim:
'The Artisan is the most powerful of magic users. She is able to shape magic, and to use it, by force of will alone. An Artist can use magic shaped by others, mould it into new magic, new art. A Magician -- or Sorcerer, Witch, Warlock -- can read, and write incantations, drawing spells from the power of words. And the Alchemist can create magic potions. He is the least of the four. Anyone, with the proper education, can be an Alchemist. The other three requires some form of talent for magic.'
Although I suspect we all are in agreement on which of the two is the most trustworthy, I shall not be committing the argument from authority fallacy, so let's have a look at some evidence:
April Ryan is no magician nor is she educated in the skill of alchemy, yet she has zero problems creating potions. It appears that the only thing you require to master the art of alchemy is follow instructions.
Roper's actual magic skills can all be attributed to his stolen soulstone; when April shatters it the wind returns, the captured souls are released and the stone spell is broken.
In 'Dreamfall' when April runs into him at the Marcurian Magic Ghetto, he claims that he is grateful to her because their previous encounter inspired him to reevaluate his life, and abandon magic all-together. He then goes on to explain that mastering advanced trigonometry was how he managed, afer five years, to escape the calculator.
DFC spoiler ahead:
The guy is obviously nothing but an opportunistic liar suffering from a case of extreme butthurt.