That's strange. I've had some huge empires with more than 100 provinces with several factions including the Romani, on a 1GB RAM Laptop, and I never had that problem.
I don't think it's the script either.
Are you sure it only happens in your Romani campaign?
You could try to start another campaign, then use cheats and blitzing to expand to the size of your current empire and see if it slows down too.
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