I'm pretty new, so take my two cents for what they're worth... but I'd lean away from adding that to the automated reactions for the sake of civility.
As much as it's sometimes tempting to have a button for showing disagreement with a post, on balance, I appreciate that there's no "thumbs down" or other overtly passive-aggressive option. Of course, current ones such as "haha" and "wow"
can be interpreted in that sense, but they're far outweighed by positive use. I think an automatic "eye roll" would yield a much higher proportion of negative use (justified or not). As
TazMan2000 points out, it is already an option in a manual reply, but I think just that little bit of required effort serves to encourage a prospective user to at least momentarily consider the virtue of biting one's tongue.
And at least if the post in question is that of a troll... a better strategy than feeding him "eye rolls" is probably to not feed him anything.