I was taught rolling back after loading a save can cause issues with variables in some situations. Since I don't know how to code I just took the advice and disabled it!
A quick lesson regarding rollback (and a link to get you deeper down the rabbit hole if you wish):
Nothing in your VN (the way you use variables) will break.
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is a quick official summary of what Python items that do not participate in rollback. Basically (for most VN cases) unless you have a dictionary or list that inherits it's attributes from other dictionaries/lists then you'll be fine. This is usually found in way more sophisticated Python function coding, a subset that is not in use by you (to date).
Bottom line: I have rollback for your VN set On in all my test builds and have never had a single issue... because you are only using integer and boolean variables anyway in your code (you are using calls instead of jumps but RenPy knows how to handle these during its rollback), you are not using custom advanced Python functions. I use many custom Python functions in the mod but write them in a way that rollback isn't a problem (so that I'm not introducing issues into a VN I mod on).
Make a bit more sense now bud? You can leave it as is (if you want) or remove it... the VN will work just fine either way. It's your call really.