For this challenge, we are given a Youtube link, https://youtu.be/CrB58R36onw. The video doesn't seem to contain anything particularly interesting as does the audio. Scrolling down a bit, we see a message in the video description.
We see that there is a link in the description. Opening the link leads us to an Imgur page.
Oof, we got rickrolled. riftCTF{rick roll'd} is just a bait and isn't the correct flag.
Looking at the hint, we see that the correct flag is in plain sight and that the flag format is riftCTFflaghere. So, we backtrack and go back to the video description and look closer.
Result: We look more closely at the fake, rickroll link, http://bit.ly/riftCTFnow_you_see_me, and see that the flag is actually right in front of us in the link.
Flag: riftCTFnow_you_see_me