I've been running this adult campaign for 2 weeks and I'm at about 2k spend. I'm curious how other people would interpret this. I'm stumped why my best ROI is at 7-8am. Maybe Caurmen can provide me with some insight? 

ROI is the most irrelevant metric in AM. (Unless you have cash flow problems)
I'd rather make $10k/day @ 20% ROI than make $1k/day @ 100% ROI
I am afraid you are not going about this the right way. In order to translate information to insights to impact, you need to start first with the right information.
For anyone to even begin to help you, at the very least you will need to track:
- What is the n size?
- What the the time zone of the audience you are running at?
- What is the time zone of your analysis?
- What is the difference in CTR over time?
- What is the difference in CVR over time?
- Have the creatives remained constant over time?
- Was the CPM/CPC constant over time?
- Are the RPLs constant over time?
- Were the placements and channels constant over time?
- How does this data compare to the other campaigns you have been running?
The chart and regression you created, while it may look insightful and precise, is in fact, from a statistical perspective not very useful for a whole host of reasons.
K.i.s.s
Yep, I'd say cmdeal is right on the money here.
Your graph has to be interpreted in the context of other info: if you can give us more info we could probably interpret more accurately. At the very least we'd need to know if this graph is in your time, or local time to the country you're running the campaign in.
On the upside, your ROI's positive 95% of the time, so that's good 
Oh, it could be the sponsor batches some leads, and they get credited when they come in?
What sponsor is it? Per Lead/ Per Sale?