This is AWESOME! I had a similar idea for my awning cover, but I was just gonna cut the pipe in 1/2, not actually notch out a portion where the awning comes out - genius!! (as a note, I have a 10' pipe cut in half in my garage that ended up way to flimsy to use...I wish I'd had your idea before, would have saved me some grief lol)
re: your question on attach to truck or standup poles...these are just my thoughts/experiences.
If this is pretty much a sun shade, and you won't be in much windy conditions, go with the freestanding (attached to truck) approach. Unless you build a strong swingarm like the Hannibal, the tarp will be somewhat 'floppy' and will easily be tossed around by the wind and collapsed by the rain. I've tested my awning using just the cheapo wally world poles attached to the roof (about 6" below where the tarp attaches to get some geometry going) and for me it just didn't seem beefy enough.
If you anticipate using this in inclement weather, I'd strongly suggest going with a the standing poles approach, just more support for rain basically.
When I made my first awning, I had a 'free' outside edge of the tarp - basically I was attaching poles to the grommets just like you have here. I found that adding a rigid outside edge (I used EMT) made 100x difference in how the awning responded to wind/rain/etc. Based on your pics, if you wanted, you could probably screw an emt conduit to the outside edge and still have enough space in your awning containment vessel for everything
The other benefit to having an outside rigid edge is that you can use a 5 gal water container and a bungee cord to hold down the awning in winds without the need for stakes - something that comes in handy in sandy or uber-rocky terrain. I can attest that 1 5 gallon water container will hold my awning down in 20-30mph winds easy.
One possible way to balance the two possibilities is to have the stakes attach somewhere lower on your truck...the further down from where the tarp attaches, the better the geometry and stronger the wind/rain resistance - think RV awning attachments.
As for rolling up the awning, it looks like the spinning end thing stick out just past your roof rack? If that's true, I would get a 1' x 3/8 solid round bar, drill a 3/8"+ hole in your rollup tube, and when you need to roll it up, just slide the round bar through the hole and spin it with both hands. When you are done you can just through the bar into the bottom of the pipe and close it all up. (does any of that make sense?)
Honestly though, gotta say it again, the way you have the tube cut and designed is AWESOME! I will definitely be stealing that idea