Pretty sure you got some other addon, I've been using ElvUI for ages as a rogue, and never had that extra energy bar (unless I download something else).
As many people have pointed out already, this addon is called Basic Resources, and it comes bundled with Assassin, rotation suggestion addon:
curse.com/addons/wow/assassin
Ok guys. Back now with some more info. Thank you for all of the replies! Ok so for this morning I've logged in and... it's gone. So... No clue how that happened. I do know this much though.
1. It was NOT the detached combobar. That looks different. This was something else.
2. Not Basic Resources. I don't have that.
3. Not VexPower. Possible to make that look in ElvUI someone said? Maybe. I've never heard of VexPower and do no have it.
4. Not Shadow & Light. I do not have that installed.
So far this morning I simply haven't seen it yet. In fact I also didn't have a normal combobar on targets. I turned that on easily enough and have had no issues at all. It's still bugging me but at least it's gone.
That addon is Basic Resources not ElvUI, I've got basic resources for a few classes and that is exactly how it looks. The addon comes bundled into quite a few other ones so it might be something completely unrelated that's actually making it appear.
What addons do you have specially installed for rogue that you don't for other classes?
Ok guys. I got it figured out finally. IT IS BASIC RESOURCES. It seems as though I had left on a druid addon called CLAW. Claw seems to include Basic Resources. (Using Curse Client to download Claw gets you both). Basic Resources does not show up in the curse client as installed. It comes and goes with CLAW. But that was it. Thank you all for the help. And now we all know. I also found out that CLAW works with rogues.:P
Thank you all again!