From what I’ve seen it’s allowed. I’ve done it myself before aswell.
However it is best to credit the person for their words. It is not required but it is a morally correct thing to do. other then that I dont see why Roblox would be against it.
Quotes aren’t nessecarially copyrighted. Most famous quotes written like what, 300 years ago would most probably not be copyrighted. I’ve done it myself and have never found a problem with it.
This should be allowed, as it does not violate copyright law or such. However, I would still be careful with them, as Roblox’s moderation system is still very strict.
All in all, you should be fine to use the quotes as long as credit for it is provided (if applicable).