Roma people have historically been very persecuted because of racism and ethnocentrism. Case in point: the holocaust killed up to 500,000 Romani people, but the actual figures are not known. Roma people are among the groups that are rarely talked about when the Holocaust is mentioned, despite losing up to 50% of their total population at the time.

Arab and North African folks are usually considered white on the US census but that isn't really an accurate picture.

Race is a social construct that doesn't have clear borders. Racial categories mostly exist as a way of creating division and limiting access to resources, to flatten the diversity of individual cultures represented by a racial category... or to inflict direct and systemic violence. The experience of being a racialized person is entirely the creation of the society that a person lives within; for example, African folks usually don't self-identify as "black," within Africa, but that's an important racialized experience that people can speak to in a place like the US.