The spirit is in the right place, but the message is not. Most people aren't sufficiently skilled to write and evaluate cryptographic primitives. That's certainly true. It's true of me, and there are a lot of noobs noobier than me out there of whom it is also true. People like us should not be writing our own primitives and putting them into production use.
But someone has to write the crypto! And the only way to learn is to try fail and reevaluate. So while I'm fine with "don't roll your own crypto" being a catchy reminder, my real advice is as follows.
Please roll your own crypto. I'm excited that you're excited about crypto! Experimenting is a great way to learn. Once you have something working, try to break it. When you break it roll a new version. When you can no longer break it, have your friends break it, and try to break theirs. Just remember, it takes time and practice to roll good crypto. So please don't put your crypto into production use until it has been reviewed by experts that you trust and experts that you don't trust. Be safe as you learn. Now go roll your own crypto!
