This answer may be a bit nebulous because the impacts of WWI aren't as clear-cut as the genocide of WWII nor as well-documented as human rights abuses behind the Iron Curtain. Admittedly this time period is not my specialty and I can't answer fully, so I'm happy to hear any corrections or additions!
One of the first things that comes to mind are the Sinti and Roma soldiers who served on both sides of the conflict. As far as I'm aware, there isn't a concentrated scholarly source about the soldiers; the most I've found are brief sentences about decorated Roma and Sinti veterans of WWI being stripped of their rights during the rise of Nazism. Most of the information I've seen comes directly from the families/descendants of the soldiers, though my own limitations means I've only learned a bit about English (Romany) soldiers and German Roma & Sinti soldiers. These soldiers signed up for most of the same reasons as many non-Roma soldiers: money/job security, pride in military service, allegiance to a specific nation, etc. (Interestingly, some of the proto-Romani were soldiers and support personnel of Indian military campaigns--while obviously not directly relevant, there is a certain cultural pride in military training and lifestyle in some Roma families.)
There are a number of legal persecutions that coincided with WWI that aren't directly related to the war itself, but nonetheless impacted Roma during the war and up to WWII. I'm specifically thinking of France's 1912 policies against "nomadism," which required "nomads" to carry a carnet d'ídentité anthropometríque (a notebook that included "two pictures of the individual’s face, front and profile, a description of family genealogy, and fingerprints; 100 blank pages followed, in which the individual was required to have an official stamp recording any entrance and exit to and from villages, towns and cities.")^1 Legal persecution had long predated WWI, it's just worth noting that the increase in these types of laws restricted Romani ability to travel (either freely or to escape conflict) without repercussion.
The Lom (sister diaspora of the Roma) are pretty closely aligned to Armenian identity and culture, with evidence that they had previously fought alongside the Armenians against the Ottoman Empire.^2 I've tried to discern whether they were also victims of the Armenian Genocide, but haven't come across anything specifically discussing Lom victims.
Wider-picture impacts can be seen in the October Revolution in Russia and the dissolution of the Ottoman Empire. In combination, they basically transformed the lives of Roma living in the Balkans as their histories became intertwined with those of Soviet nations. Treatment of Roma under Soviet rule is a much bigger topic that I'll refrain from diverging into; I bring it up because this is one of those impacts you can trace back to the outcome of WWI. There was also a migration of Christian and Muslim Roma between Greece and Turkey during the 1920s, though unfortunately I'm too unfamiliar with Ottoman history to elaborate on circumstances.
Sorry I can't give a more concrete answer! Unfortunately there just isn't much in the way of scholarly work on the subject and it varies so much between nations because of the specific laws regarding Roma.
Elena Marushiakova, Vesselin Popov, Gypsies in Central Asia and the Caucasus, p. 71