It's clear that Roman slave women had their children killed all the time.
But there are many stories about boys being killed for political purposes. There are also stories about women having their children killed - if those children were the product of adultery or as a punishment against the woman.
So it is very likely that there was non-sex selected infanticide imposed on slave women and on free women who had their children with the wrong partner.
But is there any evidence for specifically sex selective infanticide?
I can't speak for Roman society generally, but I am familiar with one specific case of sex-selective infanticide from Tel Ashkelon, Israel. We excavated a Roman/Byzantine bathhouse in Grid 38, (you can read the publication report for free at http://digashkelon.com/current-projects/, just download the massive PDF of volume 1 and you can find some descriptions of the "baby drain" on page 295, and the publication of the DNA analysis on page 537), and found literally hundreds of infant skeletons in a drain underneath the bathhouse. Why were hundreds of dead babies thrown into the drain of a bathhouse? Why were they nearly all male? (Answer, it may have also been an illegal brothel). I have sat on this drain to do paperwork many times, and am excellent friend with the person who oversaw the excavation of the infant remains. Part of the drain is actually still there, it being made of Roman concrete and all. This is a picture of the drain as it was excavated. This is a picture of it basically as it is today, taken by one of my colleagues. The drain is the concrete thing that all the people are standing on, they are standing on the same thing the guy is standing on in the other picture.
