The topic of “Django and Flask” has come up a couple times previously, see Should I use Django? for my take on the subject.
There are other threads mentioning Flask and/or ROR - you can use the site’s search tool to find them.
<opinion>
Regarding RoR, I have no opinion. I don’t know Ruby or Rails. I come to the Django world from working in Python before Rails (or Django) ever existed. Would I have grown to like RoR if I learned it first? Possibly but doubtful. For whatever reason, Ruby as a programming language just doesn’t resonate with me. I’ve looked at it enough to get the impression that I don’t want to look at it any more closely.
</opinion>