I occasionally have a similar issue with "reader's vocabulary," myself. It's certainly a problem.
I try, as much as I am able, to assume good intent when people correct my pronunciation of high-vocabulary words. Even though sometimes the correction may sound harsh (many times, because it's a quick word that can sound like a verbal jab), I've learned that most of the time, the corrector means well. As some of the commenters have already pointed out, would you really rather continue to mispronounce those words indefinitely? It's much better if the mistake is caught early on, before you use one of your "reader's vocabulary" words on an important job interview or the like.
It may be useful to try to mentally reframe your roommate's intent in this way. Even if you think that your roommate does include some unnecessary mockery in his corrections, you can "neutralize" it by smiling back and giving him a sincere "Thank you for that correction; I really appreciate that." will, ex post facto, force him to continue the conversation as if he did not intend any meanness at all. It will also make both of you look at future corrections in a more positive light.