I'll try to answer some of your questions the best I can, but I have to admit that even though I've been in the RAF program (if that's what we want to call it) for a while now, there's still some things that are a mystery to me.
There's nothing on the Dashboard pertaining to ad impressions. You can get daily reports emailed to you, but I believe you have to request them. I highly recommend getting them and/or implementing some kind of tracking/reporting within your channel. Otherwise, you're at the mercy of Roku and mistakes have been made. Having said that, Roku has made steady improvements to the process and I'm now satisfied that their numbers and my numbers match.
I don't think you can get the detail you're looking for, but I can't say for sure since I've only implemented RAF in games; I'm not displaying videos. The reports I receive are broken out by day (and I've never figured out for sure whose day that is, but I receive reports shortly after midnight Pacific time) and by channel. Maybe someone that has a video channel and receives reports can chime in on how theirs are broken out. You'd probably want to do your own tracking just to be sure. You might want to look at SetTrackingCallback
if you need that level of detailed tracking.
I use Roku entirely for filling my ads and I've been mostly satisfied. However, they only provide ads for the U.S. If you anticipate a large number of users outside the U.S. you'll want to find your own provider. There's a thread here from someone trying to find a provider without any success so far. It's hard to get the ad providers to even return an email. There's no additional steps required if you just want to go with Roku; you pretty much get them by default.
I can't help much with the current process of getting enrolled. Things were different when I first enrolled. You do want to make sure everything has made it all the way through accounting. Sometimes it seems as if the technical side and the accounting side don't communicate. If you find a contact at Roku that seems to be especially helpful, treasure that email address. 🙂
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