Simplifying the structure of your text, it could be rephrased this way:
Oggi le donne rom sono doppiamente discriminate. E quelle che vivono nei campi sono discriminate il triplo.
In the second sentence above there is a verb, sono discriminate, conjugated in the passive voice.
As in this instance, Italian passive voice can be constructed with the verb essere used as an auxiliary verb and past participle of the verb as in these examples by the linguist Luca Serianni in his book Italiano, a quite complete Italian grammar book:
(io) sono amato
(voi) sarete pregati
(tu) saresti giudicato.
All verb tenses that are costructed with auxiliary essere followed by past participle of the verb must have past participle gender and number agreed with the subject: there are no exceptions to this rule.
The subject of the second sentence above is the feminine plural pronoun quelle, so past participle must also be feminine plural. That is, it should be discriminate and not *discriminati.